Nervous system

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14 Nervous system

Rodney W.H. Walker

Introduction

In recent years there have been impressive advances throughout the whole spectrum of neurological and muscle diseases; in delineating disease entities and understanding their aetiology and pathogenesis; in diagnostic methods, particularly imaging and genetic testing; and in treatment and management. However, advances in investigations have not rendered careful clinical assessment redundant.

The fundamental importance of the clinical history and examination cannot be overemphasized. In the diagnosis of neurological disease, it is the history that is paramount, so it is even more important for this to be comprehensive than the examination. History taking has not changed significantly, but clinical neurological examination continues to evolve. Significant contributions have come from clinical assessment scales, some of which have been so successful as to have become internationally institutionalized, for example the Glasgow Coma Scale and the Mini-Mental State Examination.

A thorough neurological examination does involve doing more than is the case for other systems. Some basic neuroanatomical knowledge is necessary, but most clinical neurology need not be daunting. In new patients presenting for diagnosis, a sensible formulation of the nature of the problem on the basis of the history and examination is critical in order to request appropriate investigations, should they be necessary. Modern imaging undoubtedly has been the biggest revolution in clinical neurology in recent years, but injudicious use of imaging frequently leads to confusion, delay in diagnosis and sometimes harm. Similar considerations apply to the other major investigational modalities.

This chapter will discuss some aspects of neurological history, concentrate on neurological examination and the formulation of the nature of the neurological diagnosis and include some remarks on neurological investigations. Not covered in this chapter are coma, delirium and dementia.

The neurological history

The essentials of history taking have been covered elsewhere, but there are some points particularly salient to neurological conditions. The repertoire of neurological symptoms is actually quite limited, though perhaps larger than that of other specialties. Box 14.1 lists the usual ones, and each should be specifically enquired about in taking a neurological history.

Box 14.1 Neurological symptoms

Cognitive symptoms, especially memory impairment

Headache

Loss of awareness

Loss of consciousness

Alteration of perception, including déjà vu

Dizziness, vertigo

Loss of balance

Falls

Loss of sense of smell

Loss of taste

Loss of vision

‘Positive’ visual symptoms, including components of migraine auras, unformed and formed hallucinations

Double vision

More than double vision (polyopia, palinopsia)

Oscillopsia (a visual sensation of stationary objects swaying back and forth)

Deafness

Tinnitus

Difficulty with speech

Difficulty swallowing

Weakness

Abnormal movements of muscles (including cramp, fasciculations)

Abnormal movements of parts of the body (including tremor, dystonia, myoclonus)

Clumsiness

Impairment of control of limbs

Altered sensation

Loss of sensation

Pain

Symptoms of postural hypotension

Impairment of sexual function

Impairment of bladder control

Impairment of bowel control

The time course of evolution and sometimes resolution of neurological symptoms very frequently indicates the nature of the problem, and so this needs to be clarified as precisely as possible. Thus, sensory or motor symptoms which start abruptly and are at their most marked at, or very soon after, their onset strongly suggest a vascular causation (transient ischaemia or ischaemic or haemorrhagic stroke). In contrast, similar symptoms evolving over a few days, reaching a plateau in severity and then slowly receding typify inflammatory central nervous system (CNS) demyelination (a first episode or a relapse of multiple sclerosis). Subacute (developing over weeks to months), progressive symptoms can be caused by many kinds of pathology, but neoplasia is always a prime concern.

These statements are true enough to be clinically useful, although there are exceptions. For example, one of the reasons for requesting cranial imaging in all stroke patients is to exclude a benign or malignant tumour or other pathology which has caused a stroke-like presentation. Neurodegenerative conditions always develop insidiously with gradual progression, but occasionally patients present acutely. For example, motor neurone disease can present acutely with ventilatory failure. Alzheimer’s disease commonly becomes evident after an episode of acute delirium caused by an intercurrent illness.

Two common neurological presentations require a history not only from the patient but also, if at all possible, from others: attacks of loss of consciousness and memory impairment.

The three most common causes of attacks of reduced consciousness or awareness that lead to neurological consultations are: neurocardiogenic syncope, epilepsy and psychogenic non-epileptic attacks. It is far more informative to hear a description from a witness than to request potentially misleading and inappropriate investigations. In the setting of the emergency department, obtaining the witness’s account may involve contact by telephone; this is time well invested. Table 14.1 summarizes some points which help to distinguish syncope from seizures.

Table 14.1 Points which help to distinguish syncope from seizures involving loss of consciousness. Minor injury, incontinence and sleepiness after the event do not distinguish well

Syncope	Seizure
In neurocardiogenic syncope, characteristic prodromal features include: tinnitus, muffled hearing, dimming of vision, loss of vision while still conscious, widespread altered sensation, dizziness (may be described as spinning), lightheadedness, feeling of impending faint, weakness Marked pallor Sweating (but not in those with autonomic failure) Any convulsion is brief (seconds) Rapid recovery of lucidity and memory (registration and recall) Patient comes round on the ground where he fell A second attack immediately on being sat up after the first attack is very suggestive of neurocardiogenic syncope Neurocardiogenic syncope is commonly set off by pain, squeamishness, gastrointestinal illness, public places indoors (clubs, restaurants, trains), prolonged standing

Syncope

Seizure

In neurocardiogenic syncope, characteristic prodromal features include: tinnitus, muffled hearing, dimming of vision, loss of vision while still conscious, widespread altered sensation, dizziness (may be described as spinning), lightheadedness, feeling of impending faint, weakness

Marked pallor

Sweating (but not in those with autonomic failure)

Any convulsion is brief (seconds)

Rapid recovery of lucidity and memory (registration and recall)

Patient comes round on the ground where he fell

A second attack immediately on being sat up after the first attack is very suggestive of neurocardiogenic syncope

Neurocardiogenic syncope is commonly set off by pain, squeamishness, gastrointestinal illness, public places indoors (clubs, restaurants, trains), prolonged standing

The symptoms of focal seizure activity which precede a secondarily generalized attack may or may not be remembered after the attack is over

Usually little or no pallor

Vocalization at onset of generalized convulsion (GC)

Apnoea

Cyanosis associated with GC

Stertorous breathing

Tongue biting

Postictal amnesia – paramedical staff present when patient ‘comes round’, or patient ‘comes round’ in hospital (although he walked to the ambulance)

Patients frequently complain of memory impairment. Distinguishing between the worried well and those with real impairment is greatly facilitated by information provided by close family or other informants. In general, if a patient is brought along to a doctor by a relative who complains that the patient has memory impairment, then there is an organic disorder, usually dementia. In contrast, many, but not all, patients who come to a doctor by themselves with the same complaint have good cognitive function. Furthermore, it is the relative who can report on changes in personality, behaviour, self-care and capacity which may be crucial to the diagnosis.

The most frequent symptom leading to neurological referral is headache. It is also a common reason for attending an emergency department. The vast majority of headaches are not caused by life-threatening disorders such as aneurysmal subarachnoid haemorrhage, meningitis or brain tumour, but are caused by common primary headache syndromes, particularly migraine. Table 14.2 outlines some of the features which may help to distinguish headaches of different sorts.

Table 14.2 Headaches: points to consider in the history

Aspect of history	Feature	Diagnosis
Region/location	Focal, retro-orbital	Cluster headache
		Migraine
		Retro-orbital lesion
	Focal, frontal	Sinus pathology
	Unilateral	Migraine
		Chronic paroxysmal hemicrania (CPH)
		Hemicrania continua
	Generalized	Migraine
	Generalized	Tension-type headache
Temporal aspects	>50% of days	Chronic daily headache (chronic migraine; tension-type headache)
	Attacks of hours/days	Migraine
	Attacks of up to 1 hour	Cluster headache
	Many attacks, lasting minutes	CPH
	Attacks of seconds	Trigeminal neuralgia
	Worse on waking	Raised intracranial pressure
	Worse on waking	Sleep apnoea
	New, acute/subacute onset	Meningitis
		Abscess
		Encephalitis
	Explosive onset, severe	Subarachnoid haemorrhage (SAH)
Character and severity	Tight band around head, bland, featureless, not very severe	Tension-type headache
	Throbbing, moderately severe	Migraine
	Extremely severe, constant	Cluster headache
	Severe, stabbing, lancinating	Trigeminal neuralgia
Provoking/relieving factors	Provoked by alcohol	Migraine
	Provoked by alcohol	Cluster headache
	Occur at night, start in sleep	Migraine
		Cluster headache
		Hypnic headache
	Relieved by sleep	Migraine
	Triggered by touching or moving the face	Trigeminal neuralgia
	Caused by cough	Chiari malformation
	Caused by cough	Idiopathic cough headache
	Exertion	Exacerbates migraine
	Exertion	Benign exertional headache
	Orgasm	Benign coital headache (SAH has to be excluded in a severe single attack)
Associated symptoms	Nausea, vomiting, photophobia, phonophobia	Migraine
	Migraine aura (visual, sensory, etc.)	Migraine
	Neck stiffness, photophobia, vomiting, symptoms of fever	Meningitis
	Tear production ipsilateral to a unilateral headache	Migraine
		Cluster headache
		SUNCT*
	Ipsilateral conjunctival injection	Cluster headache
	Ipsilateral conjunctival injection	SUNCT*
	Visual obscurations	Raised intracranial pressure with papilloedema
	Persistent focal neurological symptoms	Intracranial lesion
General health	Indications of systemic neoplasia	Metastasis
General health	Polymyalgia and weight loss	Giant cell arteritis

* SUNCT, short-lasting, unilateral, neuralgiform headache attacks with conjunctival injection and tearing (a rare disorder).

Vertigo (a hallucination of movement) is an important symptom and requires careful characterization. It indicates a disorder of one or both labyrinths, vestibular nerves, vestibular nuclei in the brainstem or, rarely, the cerebrum. A clear-cut description of a spinning feeling usually signifies true vertigo. Patients are more likely to complain of dizziness or giddiness than vertigo, and both dizziness and giddiness mean different things to different patients, including vertigo, oscillopsia (a visual sensation that stationary objects are swaying back and forth), lightheadedness, loss of balance or even sometimes headache. It is always important to establish whether a patient with vertigo has positional vertigo. Enquiring whether the patient’s symptom is provoked by sitting from a lying position or standing from a sitting position will not distinguish vertigo from postural hypotension or ataxia, as all give rise to symptoms on rising. Symptoms brought on by lying down or turning over in bed or looking up at a high shelf or the sky more certainly signify real positional vertigo. It is not uncommon for patients with loss of balance to complain of dizziness; such patients will spontaneously comment that they feel secure sitting in a chair but dizzy as soon as they stand up and move around.

Focal weakness is self-explanatory. Many patients complain of feeling generally weak when they have no loss of muscle strength at all. Some patients become weak without realizing it. Thus, patients with unilateral or bilateral quadriceps weakness may present with falls rather than complain of weakness. Patients with bilateral ankle dorsiflexion weakness may complain of being off balance or of tripping rather than weakness. Exertional weakness or worsening of weakness is characteristic of neuromuscular junction disorders, but also occurs in cauda equina compression (spinal canal stenosis), spinal cord compression (cervical spondylotic myelopathy) and in multiple sclerosis and sometimes other disorders, so it is not specific but can be diagnostically helpful and so should be asked about.

Sensory symptoms may be negative (a reduction or absence of normal sensation) or positive (an abnormal sensation which is felt, e.g. buzzing, tingling, ‘pins and needles’, pain). In ordinary usage, the word numb would seem to be unambiguous, but some patients who are weak without sensory loss refer to numbness (particularly in Bell’s palsy) and, conversely, patients with sensory migraine auras may be misdiagnosed as having hemiplegic migraine because of their impression of paralysis even though they can move the affected limbs. Patients who seem imprecise have some justification; the Shorter Oxford Dictionary defines numb as ‘deprived of feeling, or of the power of movement’ so it is important to clarify exactly what the patient is describing.

As a rule, transient ischaemic attacks which involve the parietal cortex give rise to brief negative sensory symptoms. Conversely, focal sensory seizures are characterized by positive sensory symptoms.

Most organic neurological disorders which give rise to sensory symptoms involve structural or functional damage to nerves somewhere, whether it be in peripheral nerves, nerve roots, spinal cord or brain. Hypersensitivity (hyperaesthesia) to all modalities of sensation is therefore improbable or impossible. Patients who appear to have very sensitive skin as a result of a lesion (e.g. herpes zoster radiculitis) have combinations of paraesthesia, hypoaesthesia, dysaesthesia, allodynia, hyperalgesia and hyperpathia. Some of these terms are not without their ambiguities. Table 14.3 provides a definition for each.

Table 14.3 Nomenclature of cutaneous sensory symptoms

Hypoaesthesia	Reduced cutaneous sensation of any modality
Paraesthesia	Spontaneous abnormal sensation including, tingling, pins and needles and pain
Neuralgia	Pain in the distribution of a nerve or nerve root
Dysaesthesia	An abnormal perception of a sensory stimulus, e.g. touch causes tingling or pain
Allodynia	Pain caused by a stimulus that does not normally cause pain
Hyperalgesia	An abnormally intense perception of a mildly painful stimulus
Hyperpathia	Perseveration, augmentation and, on occasion, spread of pain
	The pain threshold is normal or sometimes high
	In this, the threshold for perceiving pain may be raised and there may be delay in perceiving a painful stimulus, but once perceived, the pain is severe and prolonged and may spread
Hyperaesthesia	An ambiguous term, best avoided

Neurological examination is poor at identifying and characterizing disorders of the autonomic nervous system, making it particularly important that autonomic function (including bladder and bowel control and sexual function) is addressed in the history.

The neurological examination

Aspects of neurological examination can start from the moment the patient is first encountered, before and during the taking of the history, such as noting an abnormality of gait, difficulties with speech, parkinsonism or a hyperkinetic movement disorder. There is no such thing as a comprehensive neurological examination – it would take hours or days. However, too many patients without neurological symptoms have no neurological examination at all, which on occasions proves regrettable. Consider, for instance, the case of a man who develops areflexic weakness some days after a hernia operation. How helpful would it be to know that the reflexes had been normal at the time of preoperative clinical clerking? A suggested minimal neurological examination for non-neurological patients would be: assessments of the binocular visual fields, the eye movements, the biceps, triceps, knee and ankle reflexes, the plantar reflexes and funduscopy. Most patients attending for a neurological consultation (with problems such as headache or epilepsy) have no neurological signs. A minimal routine neurological examination for such patients should include assessments of vision, the cranial nerves, motor and sensory examination and examination of gait. Bear in mind that many patients with early cognitive impairment are adept at concealing it, so that without probing, it can be missed.

For most patients, it is best to be systematic with regard to neurological examination, adhering to a routine well rehearsed by the examiner and familiar to those with whom the examiner will communicate. Thus, even if the patient’s problem is foot drop, it is entirely valid to start with examination of cranial nerves, but sensible to explain to the patient that you are going to start at the top and work down. Certain situations require flexibility; patients with any degree of impairment of consciousness need assessment of their delirium or coma from the outset. In patients with cognitive impairment, it is best to start the examination with cognitive assessment. It is important in all neurological patients to pay attention to and document mobility, and in patients presenting with a gait disorder it is appropriate to examine the gait first. For most other patients, an appropriate order of examination is: cranial nerves, speech if necessary, motor system, sensory system and gait, followed by cognitive testing if relevant.

Cranial nerve examination

Examination of the twelve cranial nerves actually involves an assessment of much more than just the nerves and nuclei, particularly in respect of the sensory visual system and eye movements. The naming and numbering of cranial nerves and their nuclei is in some measure idiosyncratic and confusing; for example, there is no olfactory nerve as such and the eighth cranial nerve is actually two nerves, as is the seventh. Within the brainstem, trigeminal sensory nuclei receive fibres not just from the fifth cranial nerve but also from the seventh, ninth and tenth nerves.

The olfactory (I) nerves

Olfactory receptor cells are bipolar sensory neurones situated under the nasal epithelium. Their central axons project in numerous bundles, not a discrete nerve, up through the cribriform plate of the skull into the olfactory bulb on the inferior surface of the frontal lobe. These project via the olfactory tract to parts of the temporal lobe and frontal lobe.

Examination of the olfactory nerves

For ordinary clinical purposes, olfaction is tested using a small number of bottles containing either a fragrant or pungent smelling substance such as lemon, clove or asafoetida. Each nostril should be tested separately. A necessary precondition is that a rhinological disorder does not preclude the test. Ideally the patient should identify the smell rather than just report that it can be smelt. There is little value in routinely testing olfaction; it is uncommon to detect an abnormality and even less common for an abnormality to contribute to a diagnosis. A subfrontal tumour such as a meningioma may cause unilateral anosmia, but other features of the history and examination will mandate the imaging which should establish that diagnosis. Subfrontal meningiomas can cause bilateral anosmia, so imaging is indicated in a patient presenting just with anosmia, unless another cause is clearly evident. Olfactory nerve fibres passing through the cribriform plate are not uncommonly sheared as a result of head injury, frequently leading to permanent bilateral anosmia. Anosmia is commonly neurodegenerative, occurring particularly in Lewy body disease, so its presence in a patient with parkinsonism increases the likelihood that the patient has idiopathic (Lewy body) Parkinson’s disease. Endocrinologists test olfaction when Kallman’s syndrome is suspected.

The optic (II) nerves

The optic nerve runs from the back of the globe of the eye to the apex of the orbit and into the skull through the optic canal to the optic chiasm, where it is joined by the optic nerve from the other eye. Directly above the optic chiasm is the hypothalamus. Directly below is the pituitary gland. The pituitary stalk runs from the hypothalamus to the pituitary gland just behind the optic chiasm, between the optic tracts. Sensory afferents from all points of the retina run in the nerve-fibre layer on the inner surface of the retina to enter the optic nerve at the optic disc. Fibres from the temporal retina (nasal visual half-field) are placed laterally while those from the nasal retina (temporal visual half-field) are medial. Fibres from the upper half of the retina run in the upper half of the optic nerve. At the optic chiasm, fibres from the nasal half of the retina (temporal visual half-field) cross (decussate) to the contralateral optic tract, while the fibres from the temporal half of the retina do not cross but proceed posteriorly into the ipsilateral optic tract (Fig. 14.1). Starting within the chiasm and continuing further posteriorly within the optic tract, fibres which convey matching information from each eye (i.e. homonymous fibres, representing equivalent parts in the temporal retina for one eye, nasal retina for the other eye) become aligned with each other. Thus, each optic nerve conveys information from its respective eye, but every part of the sensory visual system behind the optic chiasm on each side deals with vision for the contralateral binocular visual half-field.

The majority of optic tract fibres pass, via the lateral geniculate nucleus, to the occipital cortex. The lower part of the visual radiation transmits visual information from the inferior temporal retina of the ipsilateral eye and inferior nasal retina of the other eye. A few optic tract fibres pass via the superior colliculus to the midbrain to mediate the afferent limb of the pupillary light reflex via connections to the Edinger-Westphal nuclei.

Funduscopy

This technique is described in Chapter 19. The neurological examination focuses on papilloedema, optic atrophy or pigmentary retinal degeneration and vascular disease.

The oculomotor (III), trochlear (IV) and abducens (VI) nerves – eye movements

Abnormalities of eye movements may result from disorders of the cerebral hemispheres, brainstem, cerebellum, cranial nerves III, IV and VI, the neuromuscular junctions between oculomotor nerves and eye muscles, the eye muscles themselves and from lesions affecting the structure and contents of the orbits. Their importance in neurological and general physical examination is therefore evident.

The nucleus for the third cranial nerve is in the midbrain (Fig. 14.2) and emerges ventrally (anteriorly), medial to the cerebral peduncle, passing forward through the cavernous sinus to the superior orbital fissure. In the orbit, the superior ramus supplies superior rectus and levator palpebrae superioris. The inferior ramus supplies inferior rectus, inferior oblique and medial rectus and parasympathetic fibres from the inferior ramus pass to the ciliary ganglion and thence to the ciliary muscle and the pupil sphincter.

Figure 14.2 A diagram of the midbrain. Note the dorsally positioned third nerve nuclei. Vascular territories are shown on the left.

The fourth nerve nucleus lies just caudal to the third nerve nucleus in the brainstem. The nerve fibres of the fourth nerve decussate. The nerve starts on the dorsal aspect of the brainstem and passes around the brainstem through the cavernous sinus and superior orbital fissure to the superior oblique muscle. Consequent upon the decussation of fibres, the right trochlear nucleus innervates the left superior oblique and vice versa.

The sixth nerve nucleus is beneath the floor of the fourth ventricle in the pons (Fig. 14.3). Nerve fibres run forward (ventrally) through the pons emerging at its lower border, then up the skull base and forward through the cavernous sinus to the superior orbital fissure and into the orbit to supply the lateral rectus muscle. The nerve is long, thin and very susceptible to dysfunction, most notably in the setting of raised intracranial pressure of any aetiology, which may give rise to either unilateral or bilateral sixth nerve lesions. This is referred to as a ‘false localizing sign’, since a focal mass lesion causing raised intracranial pressure may be remote from the sixth nerves and their nuclei or there may be no focal cause of the raised pressure at all (e.g. idiopathic intracranial hypertension).

Figure 14.3 A diagram of the fifth, sixth and seventh nerve nuclei in the pons. Note how the nerve fibres of VII loop round the nucleus of VI.

Table 14.4 and Figure 14.4 outline the actions of each eye muscle.

Table 14.4 Actions of the eye muscles

Figure 14.4 A diagram showing which muscles elevate and depress the abducted and adducted eye.

Terminology in eye movements

Horizontal movement of the eye outwards (laterally) is termed abduction and inwards (medially) is termed adduction. Vertical movement upwards is termed elevation and downwards is depression. The eye is also capable of diagonal movements (version) at any intermediate angle. Rotary movements are those in which the eye twists on its anterior–posterior axis. Convergence refers to adduction of both eyes to fixate on a near object. Lateral rotation of the head causes replex rotation of the eyes in the opposite direction (internal rotation of one eye, external rotation of the other). A squint (the eyes point in different directions) is described as convergent or divergent strabismus, depending on whether the eyes point towards or away from each other. Saccades are abrupt, rapid small movements of both eyes, such as those needed to shift fixation from one object to another. Nystagmus denotes rhythmic oscillations of one or (more usually) both eyes. In pendular nystagmus, the movement is slow in both directions. In jerk nystagmus, there is a slow phase in one direction and a fast phase in the opposite direction. By convention, the direction of nystagmus is the direction of the fast phase, but the defect is in fact the slow phase and is either an abnormal deviation of the eyes or a failure of the eyes to maintain position, and the fast phase is a compensatory saccade aimed at restoring the correct position of the eyes. Some types of nystagmus are outlined below.

Examination of eye movements

As with every other component of examination, the detail in which the eye movements are examined depends on whether there are relevant symptoms and whether abnormal signs are likely to be present. Ask the patient to keep his head still (assist him by putting your left hand on his head to steady it) and then to look at your right index finger held directly in front of his eyes at about half a metre distance. In the primary position of gaze, look for any visible abnormality of the alignment of the two eyes (an affected patient may or may not complain of double vision) and any pendular or vestibular nystagmus (see below). Now move your finger to the right, left, up and down in a large ‘H’ pattern. The pursuit eye movements which are elicited should precisely follow your finger at the appropriate constant velocity. Eye movements which are ‘broken up’ into a series of short saccades indicate a brainstem or cerebellar lesion affecting eye movement control. Patients with diplopia will experience their diplopia at some point (or at all times) during this simple test. Gaze-evoked and vestibular nystagmus will be observable (see below). When looking for nystagmus, it is important not to get the patient to look too far in any direction since, at the extremes of gaze, nystagmus can be normal as the patient struggles to deviate his eyes beyond what is possible. Look for nystagmus at about 30° away from the primary position of gaze.

Diplopia testing

If a patient complains of double vision, first establish that it is true diplopia and not monocular diplopia. In patients who have obvious, easily visible paresis of movement of one or both eyes, the reason for diplopia is self-evident (Fig. 14.5).

Figure 14.5 Right third nerve palsy. The patient had a complete ptosis. The eyelid is lifted to reveal a dilated pupil with external strabismus.

(Reproduced with permission from Mir 2003 Atlas of Clinical Diagnosis, 2nd edn, Saunders, Edinburgh.)

Diplopia develops with even very subtle misalignment of the eyes, which cannot be seen on simple inspection. In this situation, if the ophthalmoparesis affects just one eye, it is possible to work out which eye muscles are underactive by diplopia testing. The true image is that generated by the eye with normal movements. The false image is that generated by the eye with the paretic muscle or muscles. For example, if a patient develops double vision on looking to the right, with horizontal separation of the images, the false image will be the one further out to the right. This is true whether it is the right eye which does not abduct adequately (right lateral rectus weakness) or if it is the left eye which does not adduct adequately (left medial rectus weakness). If this does not seem immediately clear, consider the extreme case: one eye moves, the other does not. An image (an examiner’s finger or a white pinhead) moves to the patient’s right. The image remains in the middle of the field of the eye which moves, but moves progressively to the right of the field of the eye which does not. The same rule applies in all directions of gaze. Diplopia is always maximal in the direction in which the weak muscle has its purest action (see Table 14.4).

The severity of the diplopia should be assessed in eight positions: looking to left and right, up and down, and obliquely up and down to the left and obliquely up and down to the right. To work out which muscle is underactive, where the diplopia is maximal, cover each eye in turn and get the patient to tell you which of the two images disappears. Inconsistent answers are common, however, and the assistance of an ophthalmologist or optometrist is frequently desirable. The features of lesions of the third, fourth and sixth cranial nerves are summarized in Table 14.5.

Table 14.5 The effects of lesions of the oculomotor (III), trochlear (IV) and abducens (VI) nerves

Affected nerve	Signs	Comment
Oculomotor	Paresis of adduction (medial rectus)	The eye becomes abducted because of unopposed action of lateral rectus, and slightly depressed because of action of superior oblique
	Paresis of elevation (superior rectus and inferior oblique)	The pure depressor action of superior oblique cannot be tested because the eye cannot be adducted
	Paresis of elevation (superior rectus and inferior oblique)	Intorsion of the eye on attempted down gaze indicates intact trochlear nerve and superior oblique function
	Paresis of depression (inferior rectus)
	Ptosis due to paresis of levator palpebrae superioris	With complete ptosis, there is of course no diplopia
	Dilated, unreactive pupil	This feature is not present in pupil-sparing lesions (microvascular lesions of nucleus or nerve)
Trochlear	Paresis of superior oblique	Extorsion of the eye due to unopposed action of inferior oblique leads to diplopia such that a vertical line looks V-shaped
Trochlear	Paresis of superior oblique	The patient compensates with a head tilt to the side opposite the lesion, intact intorsion on that side tending to correct the diplopia
Abducens	Paresis of lateral rectus	Horizontal diplopia

In assessing patients who have double vision, it is best first to establish which muscles appear to be weak, and then try to decide what the nature of the problem is likely to be, taking into consideration all the physical signs. Thus, impairment of eye movements in one eye in combination with proptosis of that eye may occur because of mechanical restriction of eye movements by an intraorbital lesion. Weakness of muscles in both eyes with different patterns of involvement of the muscles in the two eyes is likely to be due to a disorder of the muscles themselves (orbital myositis, thyroid eye disease) or due to ocular or generalized myasthenia. The pupils will not be involved. Bilateral, asymmetrical combinations of cranial nerve lesions are relatively uncommon (neoplastic infiltration, cranial polyneuritis). Bilateral sixth cranial nerve lesions are common, usually but not exclusively as a feature of raised intracranial pressure. Multiple oculomotor neuropathies in one eye direct attention to the superior orbital fissure and the cavernous sinus (see Box 14.2).

Box 14.2 Cranial nerve involvement in lesions of the cavernous sinus and superior orbital fissure

1 Lesion of the cavernous sinus (e.g. internal carotid aneurysm; internal carotid artery dissection; meningioma):

– potential involvement of cranial nerves III, IV, VI, V₁ (ophthalmic division), V₂ (maxillary division) and sympathetic pupillodilator nerve fibres

– cavernous sinus thrombosis combines the above with proptosis, chemosis, papilloedema and visual failure

2 Lesion of the superior orbital fissure (e.g. Tolosa Hunt syndrome):

– potential involvement of III, IV, VI and V₁ (ophthalmic division)

– extension into the orbit may lead to involvement of the optic nerve

Horizontal gaze paresis; internuclear ophthalmoparesis

Neural control of voluntary lateral gaze to the right starts in the left cerebral hemisphere, such that a large left cerebral hemisphere lesion may be associated with failure of right gaze and a tendency for the eyes to deviate to the left (the side of the lesion). Output runs to the right paramedian pontine reticular formation (PPRF); hence,a right-sided pontine lesion may involve a right gaze paresis. Output from the right PPRF goes to the right sixth nerve nucleus, resulting in right eye abduction, and across, via the left medial longitudinal fasciculus (MLF), to the left third nerve nucleus, resulting in simultaneous left eye adduction. Attempted right gaze in the setting of a left MLF lesion results in abduction of the right eye, but failure of adduction of the left eye – an internuclear ophthalmoparesis (INO) (see Fig. 14.6). Bilateral MLF lesions give rise to bilateral INO, in which case, with lateral gaze in either direction, only the abducting eye moves normally. Commonly, nystagmus is seen in the abducting eye. The pathway for adducting both eyes for near vision is separate, and sometimes in bilateral INO preservation of adduction of the eyes for near vision can be demonstrated, proving that the problem is not bilateral medial rectus weakness.

Figure 14.6 (A) A right internuclear ophthalmoparesis. (B) A diagram of the pathways for horizontal gaze. The command for left gaze originates in the right cerebral hemisphere. Descending nerve fibres decussate to reach the left pons. Lesion 1 produces a left horizontal gaze paresis. Lesion 2 produces a right internuclear ophthalmoparesis. Lesion 3 produces the ‘one and a half’ syndrome: a left gaze paresis and left internuclear ophthalmoparesis (failure of adduction of the left eye on right gaze) – only abduction of the right eye on right gaze remains. NPH, nucleus prepositus hypoglossi; MLF, medial longitudinal fasciculus; PPRF, paramedian pontine reticular formation.

Vertical gaze pareses

The neural control of upgaze and downgaze is complex. Ultimately, output for upgaze is via components of the third nerve nucleus mainly to the superior rectus and inferior oblique muscles bilaterally. The output for downgaze is from the third and fourth nerve nuclei to the inferior rectus and superior oblique muscles, respectively. In general, defects of upgaze or downgage localize rather poorly, but lesions such as pineal tumours which compress the midbrain and bilateral descending connections from the hemispheres often cause upgaze paresis.

Non-paralytic strabismus

Neurologists need to be able to recognize non-paralytic strabismus. Decompensation of a longstanding squint may be a cause of acquired diplopia, but this is an ophthalmological problem and it is covered in Chapter 19.

Testing saccadic eye movements

Getting a patient to follow a moving finger tests pursuit eye movements. It takes very little time to test saccadic eye movements and useful signs may be detected. First, simply ask the patient to keep his head still and look to the left, to the right, up and down. Then hold your hands up in front of the patient, one in the primary position of gaze, the other to the side, with palms facing the patient, fists closed. Ask the patient to keep his head still. Open the fist of the hand in front of the patient and ask him to look at it. Then close that fist and open the other and ask the patient to switch his gaze to the hand at the side. By alternating which hand is open you can get the patient to refixate briskly to and fro. Then check the other side. These manouevers test saccadic movements; in disease, saccades may be slowed or interrupted. They are also the best way of detecting a mild internuclear ophthalmoparesis.

Supranuclear gaze pareses

Reflex eye movements related to head movements are generated and organized by vestibular, cerebellar and brainstem systems, whereas voluntary gaze is initiated in the cerebral hemispheres. A patient’s gaze paresis is therefore supranuclear if reflex eye movements are intact. Take a patient with selective paresis of downgaze. If brisk backward rotation of the head (extension of the neck) produced reflex depression of both eyes, a supranuclear lesion would be inferred. In practice, this is often not easily achieved since the relatively common disorder giving supranuclear downgaze paresis is progressive supranuclear palsy, a condition in which there is also axial rigidity affecting neck movements.

Peripheral vestibular nystagmus

This occurs in lesions of the labyrinth or vestibular nerve. Normally there is tonic input to the brainstem vestibular nuclei from the periphery. Loss of this tonic input leads to deviation of the eyes towards the affected side (slow phase) with fast-phase nystagmus directed to the opposite side. In mild lesions, the nystagmus is only seen when the eyes look in the direction of the fast phase. In more severe lesions, the nystagmus is seen with the eyes in the primary position of gaze or even when looking away from the direction of the fast phase. Usually the nystagmus is of high frequency and relatively low amplitude.

Gaze paretic nystagmus

This is a gaze-evoked nystagmus in which the eyes are not able to maintain a position away from their primary position, so the slow phase is a drift back to the primary position while the fast phase is in the direction of gaze. In the primary position, the eyes are still. The nystagmus may be of large amplitude and low frequency. Drug-induced nystagmus (alcohol, benzodiazepines, antiepileptic medication) is of this sort and is seen in all directions of gaze. Structural brainstem or cerebellar lesions may cause asymmetric gaze paretic nystagmus. In cerebellar hemisphere lesions, the nystagmus may be unidirectional with the fast phase towards the side of the lesion.

Upbeat nystagmus (fast phase upwards) may occur with lesions at various locations in the brainstem and with cerebellar vermis lesions. Downbeat nystagmus is characteristic of cervicomedullary junction lesions such as Chiari malformations, but can also be seen with cerebellar degenerations.

Congenital nystagmus

The rule here is that the nystagmus is horizontal, even when the patient looks up or down. On left gaze, it is left beating, and on right gaze, it is right beating. There may be a null point at which the nystagmus is least conspicuous, but it is not necessarily in the primary position, and the eyes may not be completely still. Congenital nystagmus is damped by convergence.

Pendular nystagmus

This may be seen as a complication of congenital or acquired very poor vision. It is also seen in pontine lesions (e.g. multiple sclerosis).

The trigeminal (V) nerve

This is a mixed motor and sensory nerve. The nerve trunk emerges from the pons as sensory and motor roots.

Sensory component of the trigeminal nerve

The primary sensory neurones are in the trigeminal ganglion, just behind the cavernous sinus at the apex of the petrous bone. Central projections run in the trigeminal nerve into the pons. Figure 14.7 shows the cutaneous distribution of the three divisions of the trigeminal nerve: ophthalmic (V₁), maxillary (V₂) and mandibular (V₃). These nerves also mediate general sensation inside the mouth and nose and proprioception. The ophthalmic nerve passes through the cavernous sinus and superior orbital fissure. The maxillary nerve also passes through the cavernous sinus, but leaves the inside of the skull through the foramen rotundum. The mandibular nerve passes through the foramen ovale.

Figure 14.7 Areas of cutaneous innervation of the head and neck by the three divisions of the trigeminal nerve and the upper cervical nerve roots.

Afferents mediating touch sensation pass to the principal sensory nucleus of the trigeminal nerve in the pons. Pain and temperature afferents go into the spinal tract and pass caudally into the medulla and into the spinal nucleus of the trigeminal nerve, which extends down from the medulla as low as the upper cervical spinal cord. Thus, lesions in the medulla can give rise to dissociated sensory loss in trigeminal territory (loss of pinprick sensation with preserved light touch sensation).

Motor component of the trigeminal nerve

Motor nerve fibres from the motor nucleus in the pons run in the motor root of the trigeminal nerve, bypassing the trigeminal ganglion to enter the mandibular nerve. They supply the muscles of mastication: masseter, temporalis and the lateral pterygoids.

Trigeminal territory sensory loss

Patients with impaired sensation on one side of the face may have a trigeminal nerve lesion, a trigeminal nucleus lesion or a lesion of central trigeminal sensory pathways. Not uncommonly, unilateral facial sensory symptoms remain unexplained, which does not necessarily make them ‘non-organic’. Much is made of distinguishing between patients whose distribution of sensory loss is anatomical and those in whom it is not. Sensory loss which ends at the jaw line and at the hairline would be regarded as non-anatomical but too much dogma may be unwise – patients are often not very careful reporters of exactly where their sensory symptoms are. Clearly defined symptoms of reduced sensation render examination almost redundant, but the area of hypoaesthesia can be delineated in the same way as sensory loss anywhere else using a pin and testing from a numb area outwards towards where sensation is normal.

The corneal reflex

A sensory stimulus applied to the cornea causes a reflex blink which cannot be suppressed; its absence on one side establishes unequivocally the presence of a trigeminal lesion. Patients with an anaesthetic cornea are at risk of corneal injury, so it is important to identify affected individuals by testing patients who very clearly have symptoms and other signs of a trigeminal lesion. It is also an important test in coma. The test is uncomfortable and should not be part of a ‘routine’ neurological examination. The presence of a normal corneal reflex does not mean that there is no lesion of the trigeminal nerve or its connections.

Explain to the patient what is going to happen. Ask him to look in such a direction that the eyes are wide open. Using the corner of a clean tissue, touch the centre of the patient’s cornea, approaching from the side. The normal response is a brisk blink. Some use cotton wool, but there is a risk of strands getting stuck in the eye because of the blink. In coma, a drop of saline applied to the cornea is a good stimulus. Remember that if there is ipsilateral facial paralysis (e.g. Bell’s palsy), the reflex will be absent on the affected side, but will be readily seen on the other side.

Testing the motor component of the trigeminal nerve

Look for wasting of the temporalis and masseter muscles. Feel for contraction of the masseter muscles when the patient clenches his jaw. Ask the patient to open his mouth; the lateral pterygoid muscles on each side draw the mandible forward, such that a severe lesion of the trigeminal nerve will lead to deviation of the jaw towards the side of the lesion due to weakness of the pterygoid muscles on the affected side. The pterygoid muscles may be further tested by asking the patient to push his open jaw sideways against your hand.

The jaw jerk

This can be a useful reflex to test, but it is usually examined along with the tendon reflexes of the limbs (see below). Its usefulness is when it is pathologically brisk in a patient with a spastic tetraparesis, because it points to the site of the causative lesion being in the cerebral hemispheres (e.g. diffuse small vessel cerebrovascular disease, amyotrophic lateral sclerosis or hydrocephalus) rather than the cervical spinal cord.

Ask the patient to let his jaw hang down in a relaxed manner, with the mouth slightly open. Place your index finger across his chin. Strike it lightly with a tendon hammer; reflex contraction of both masseters is the response. Sometimes an extremely brisk jaw jerk is accompanied by clonus.

The facial (VII) nerve

The facial nerve is principally a motor nerve, supplying facial muscles on one side, but it also has a small general somatic sensory and major gustatory sensory components, as well as important parasympathetic functions.

The facial nerve nucleus is in the caudal pons, lying ventrolateral to the sixth cranial nerve nucleus (see Fig. 14.3). It receives upper motor neurone input from both cerebral hemispheres. Lower motor neurone fibres from the facial nucleus first pass round the sixth nerve nucleus, then emerge from the pons to form the facial nerve. From here, it travels laterally, adjacent to the eighth cranial nerve, to the internal auditory meatus, thence to the facial canal which has a relatively long and tortuous course through the skull, emerging at the stylomastoid foramen. The nerve then passes forward into the parotid gland and divides into branches which supply all the facial muscles and the platysma muscle on one side. In the facial canal, a branch of the facial nerve supplies the stapedius muscle.

The nerve cell bodies of the sensory components of the facial nerve are in the geniculate ganglion in the facial canal. Gustatory sensory afferents from the anterior two-thirds of the tongue travel in the lingual nerve and then via the chorda tympani nerve to join the facial nerve in the facial canal. Central projections reach the medulla via the nervus intermedius between the facial and eighth cranial nerve.

The peripheral projections of the small general somatic sensory contribution innervate the tympanic membrane, external auditory meatus and tragus of the ear. This accounts for the herpetic vesicles seen in the ear in patients with the Ramsay Hunt syndrome of facial paralysis caused by herpes zoster affecting the facial nerve.

Secretomotor parasympathetic efferents leave the pontomedullary junction in the nervus intermedius which joins the facial nerve in the internal auditory meatus. Some of the parasympathetic nerves leave the facial nerve at the geniculate ganglion in the greater petrosal nerve, eventually mediating tear secretion from the lachrymal glands. Others leave via the chorda tympani nerve to reach salivary glands.

These complexities are relevant to clinical neurology because a facial nerve lesion, depending on its location, may be associated with loss of taste, hyperacusis (if stapedius is paralysed) and, in chronic lesions, ‘crocodile tears’ (i.e. inappropriate tear production when salivary glands should be activated), attributed to aberrant reinnervation of salivary and lachrymal glands.

Facial weakness occurs because of muscle disorders (invariably bilateral weakness), myasthenia (invariably bilateral but may be asymmetric early on), polyneuropathies (e.g. Guillain-Barré syndrome or vasculitis; unilateral or bilateral), facial nerve or nuclear lesions (most commonly unilateral), motor neuronopathies (usually bilateral) or upper motor neurone disorders (usually unilateral, but occasionally bilateral).

A lower motor neurone lesion affecting the whole of the facial nerve nucleus or the whole of the facial nerve will cause weakness of all muscles of one side of the face. A unilateral upper motor neurone lesion, however, will cause weakness of the lower half of the face with sparing of the upper half of the face because there is bilateral representation of the upper half of the face in the motor cortex.

Testing the facial nerve

Look for asymmetry of the face. Ask the patient to raise his eyebrows (to look astonished), to blink and then to screw both eyes up, firmly closed. On a weak side, the eyelashes will be less buried by the eyelids. Attempt to raise the patient’s eyebrows while his eyes are closed and screwed up; mild weakness may be detected. When there is severe lower motor neurone facial weakness, the patient will not be able to close the affected eye. Attempted eye closure will be accompanied by elevation of the eyes (Bell’s phenomenon). Ask the patient to blow his cheeks out, to show his teeth (or gums) and then to grimace. Observe the patient’s spontaneous smiles. (In some upper motor neurone disorders of facial muscle control, voluntary movement of the lower face is lost but smiling is relatively preserved.) Ask the patient to purse his lips together and attempt to open them using your fingers. These tests usually suffice to pick up facial weakness and to distinguish between upper and lower motor neurone disorders.

The vestibular and cochlear (VIII) nerves

These two nerves convey afferents from the vestibular apparatus and the cochlea, respectively, via the internal auditory meatus to the pontomedullary junction in close proximity to the facial nerve, reaching vestibular and cochlear nuclei in the brainstem. Acute sensorineural deafness and acute vestibular neuritis reflect separate pathologies selectively affecting each of these nerves.

Testing the vestibular and cochlear nerves

The assessment of deafness is covered in detail elsewhere (Ch. 20). At the bedside, a crude assessment of hearing can be achieved by rubbing your index finger and thumb together close to the patient’s ear, or by whispering numbers close to his ear, with the contralateral ear occluded. Rinne’s test is good for distinguishing between conduction and sensorineural deafness, as long as you use the appropriate tuning fork (frequency 512 – not the lower frequency tuning fork (128) used for testing vibration sense).

Conduction deafness is sometimes of neurological significance if an infective or neoplastic middle ear lesion has spread to affect middle or posterior cranial fossa structures.

Unilateral sensorineural deafness is an important feature of ‘cerebellopontine angle lesions’, such as acoustic neuroma or meningioma, along with variable combinations of facial weakness (facial nerve), facial sensory symptoms (trigeminal nerve), nystagmus (brainstem and vestibular nerve), ataxia (brainstem and cerebellum), and ultimately long tract signs (brainstem) and raised intracranial pressure.

Bilateral sensory deafness may be a feature of certain multisystem neurological disorders, particularly mitochondrial disorders.

The disorder variously called labyrinthitis and acute vestibular neuritis (the latter is regarded as being the more accurate designation) causes vertigo and peripheral vestibular nystagmus (see p. 293). A common symptom is positioning vertigo, most commonly benign paroxysmal positioning vertigo. Positioning vertigo and nystagmus are best elicited and tested by the Dix-Hallpike test (see Ch. 20).

The glossopharyngeal (IX) nerve

There are anatomical and functional relationships between the glossopharyngeal nerve, the vagus nerve and the cranial component of the accessory nerve. The nucleus ambiguus in the medulla (Fig. 14.8) contains the motor neurones which innervate striated muscle of the palate, pharynx, larynx and upper oesophagus, fibres running partly in the glossopharyngeal nerve, mainly in the vagus nerve and partly in the cranial portion of the accessory nerve. Situated more dorsally in the medulla, the dorsal motor nucleus of the vagus and the inferior salivatory nucleus (whose fibres join the glossopharyngeal nerve) contain preganglionic parasympathetic neurones which control glands and smooth muscle. Special visceral afferents (i.e. taste fibres from the intermediate nerve and the glossopharyngeal nerve) enter the solitary tract to end in the nucleus of the solitary tract in the medulla. General somatic sensory afferents in the glossopharyngeal and vagus nerves join trigeminal sensory nuclei.

Figure 14.8 A diagram of cranial nerve nuclei and tracts in the medulla. Vascular territories are shown on the left. ASA, anterior spinal artery; PICA, posterior inferior cerebellar artery.

The glossopharyngeal nerve rootlets emerge from the medulla just rostral to those of the vagus nerve. The glossopharyngeal nerve leaves the skull via the jugular foramen. It mediates somatic sensation of the palate and pharynx and gustatory sensation from the posterior third of the tongue, and it has autonomic secretomotor fibres which reach the parotid gland, and it supplies the stylopharyngeus muscle (which cannot be tested clinically).

Testing the glossopharyngeal nerve

In routine neurological examinations, this nerve is not tested. If there are particular clinical indications to test it, such as a symptom of pharyngeal sensory impairment, pharyngeal neuropathic pain or a lesion of the vagus nerve, pharyngeal sensation can be tested using an orange stick to touch lightly the mucosa of the posterior pharyngeal wall. This requires tolerance and cooperation on the part of the patient. Some normal individuals will gag even at the approach of a tongue depressor or orange stick. In stuporous or comatose patients, testing the gag reflex may be useful. The afferent component of this reflex involves the glossopharyngeal nerves.

The vagus (X) nerve

The rootlets of the vagus emerge from the medulla just below those of the glossopharyngeal nerve. Both nerves leave the base of the skull through the jugular foramen. The vagus nerve passes down the neck adjacent to the internal carotid artery and internal jugular vein. Motor efferent fibres supply pharyngeal muscles. The superior laryngeal nerve supplies the cricopharyngeus muscle of the larynx and conveys sensation from the larynx. Lower down in the thorax, the recurrent laryngeal nerve passes back up the neck to supply the laryngeal muscles other than cricopharyngeus. The visceral afferent and efferent fibres of the vagus nerve downstream of the recurrent laryngeal nerves are not amenable to clinical neurological examination.

Testing the vagus nerve

A patient with a proximal unilateral lesion of the vagus nerve may complain of dysphagia and nasal regurgitation of swallowed fluids. There will be weakness of the muscles of the soft palate on the affected side. Attempted voluntary elevation of the soft palate (ask the patient to say ‘Ahh’, preferably fairly high pitched) reveals the weakness of elevation of the palate on the affected side, along with deviation of the uvula to the unaffected side, because of the unopposed action of the palatal muscles on that side. In addition, ipsilateral vocal cord paresis will lead to dysphonia. Bilateral lesions of the vagus nerves will invariably be associated with dysphagia. (Bilateral palatal weakness is not commonly due to bilateral vagus lesions but rather to more diffuse disorders such as polyneuropathy or myasthenia gravis.) The effects of bilateral lesions of innervation of the larynx vary depending on whether there is weakness mainly of vocal cord abduction or adduction or both. Bilateral abductor weakness puts the patient at risk of stridor and respiratory obstruction. Bilateral adductor weakness leads to dysphonia and inability to generate a normal explosive cough (the cough which the patient can manage is described as a bovine cough).

The accessory (XI) nerve

The cranial accessory nerve is formed of nerve fibres from the nucleus ambiguus and they soon leave the accessory nerve to rejoin their equivalents in the vagus nerve. The spinal accessory nerve consists of motor nerve fibres from the cervical spinal cord (C2-6); instead of leaving the spinal cord in spinal roots, they pass rostrally up into the medulla and emerge as the accessory nerve which, along with the glossopharyngeal and vagus nerves, passes through the jugular foramen. The spinal accessory nerve supplies the sternocleidomastoid muscle and the upper part of the trapezius muscle.

Testing the accessory nerve

The left sternocleidomastoid muscle contributes to rotation of the head to the right and vice versa. Weakness of the left sternocleidomastoid is therefore assessed by asking the patient to turn his head to the right with force, while the examiner opposes the rotation with the left hand, pushing carefully against the right side of the face. Failure of contraction of the muscle can be seen. Weakness of the upper part of trapezius is one of the causes of winging of the scapula, the other being weakness of serratus anterior due to a lesion of the long thoracic nerve (see p. 305). Scapular winging due to trapezius weakness is most commonly caused by a lesion of the accessory nerve in the posterior triangle of the neck, often iatrogenic related to surgical excision of a lymph node.

The hypoglossal (XII) nerve

The hypoglossal nucleus in the medulla contains motor neurones which innervate tongue muscles. The nerve leaves the lower medulla, passing through the hypoglossal canal to leave the base of the skull, then down and forward to reach the tongue.

Testing the hypoglossal nerve

A unilateral hypoglossal nerve lesion in the acute stage leads to weakness of tongue muscles on the affected side. Attempted protrusion of the tongue results in deviation of the tongue toward the weak side. A chronic lesion will be associated with visible muscle atrophy of the affected side of the tongue. Bilateral wasting and weakness of the tongue with fasciculation is usually due to the progressive bulbar atrophy of motor neurone disease (Fig. 14.9).

Figure 14.9 Bilateral fasciculation and wasting of the tongue in motor neurone disease. The tongue was fasciculating.

Speech

Dysphonia is an abnormality of production of vocal sounds. Vocal cord paresis therefore causes dysphonia. Parkinson’s disease may cause dysphonia and certainly hypophonia, a low volume voice.

Dysarthria is an abnormality of articulation, for which neurological disease is an important cause. Those with a musical ear may be good at distinguishing spastic from cerebellar dysarthrias, but experienced neurologists sometimes get this wrong. The important thing is to detect mild dysarthria and look for other signs which will clarify its basis, and to consider that a patient who has dysarthria may, more importantly, have dysphagia.

Spastic dysarthria

An upper motor neurone disorder affects the tongue, pharynx and facial muscles. Tongue movements are slow, the jaw jerk is brisk and facial stretch reflexes may be present. If part of a pseudobulbar palsy due to diffuse small vessel cerebrovascular disease or motor neurone disease, there will be associated cognitive abnormalities and limb signs.

Cerebellar (ataxic) dysarthria

Look carefully for nystagmus and other eye movement disorders, and for limb and gait ataxia.

Parkinsonism (hypokinetic dysarthria)

As well as dysphonia, there may be dysarthria and other disorders of speech and language such as acquired stutter.

Bulbar palsy (flaccid dysarthria)

Bulbar refers to the medulla oblongata, and bulbar palsy denotes any weakness of muscles supplied by the seventh to twelfth cranial nerves from the pons and medulla. Dysarthria and dysphagia are the main manifestations. Palatal weakness allows nasal escape of air during production of plosive sounds. There are many causes, ranging from muscle disorders, myasthenia gravis and polyneuropathies to lower motor neuronopathies. In myasthenia, fatigue may be evident, the dysarthria developing as the patient talks.

Severe upper motor neurone lesions such as strokes will produce dysarthria and it may also be a feature of certain dysphasias.

Motor system

For the purposes of clinical neurological examination and interpretation of neurological signs, the anatomical considerations can be kept simple. The motor neurones whose axons terminate at neuromuscular junctions and which activate voluntary striated muscle contraction are situated in the anterior horns of the spinal cord grey matter and in motor cranial nerve nuclei. These are the lower motor neurones. Upper motor neurones are those situated in the cerebral cortex whose axons leave the cortex to control, directly or indirectly, the lower motor neurones. Some of these are in the somatotopically organized primary motor cortex (Fig. 14.10) in the precentral gyrus at the back of the frontal lobe, but the distribution of upper motor neurones in the cortex is much wider than just the primary motor cortex, and includes the supplementary motor area and premotor cortex in the frontal lobes. The cerebral control of posture and movement involves widely distributed cortical motor systems. Crucial also are circuits involving the basal ganglia and cerebellum. Output from the cortex is either direct to motor neurones via corticospinal and corticobulbar tracts or indirect via projections to the brainstem which has major influences by various pathways.

Figure 14.10 Somatotopic representation in the primary motor cortex.

The corticobulbar and corticospinal tracts pass via the internal capsule and cerebral peduncle to the ventral pons. The corticobulbar tract projects to motor nuclei of cranial nerves V, VII, IX, X and XII bilaterally. The corticospinal tract continues in the medullary pyramid. The majority of corticospinal tract fibres decussate in the lower ventral medulla, passing into the lateral corticospinal tract of the spinal cord to innervate contralateral spinal motor neurones. These fibres control movements of the limbs. A minority of corticospinal tract fibres do not decussate but proceed straight on into the spinal cord in the anterior corticospinal tract, to project to motor neurones bilaterally. They control axial muscles involved in posture.

The fundamental effect of a lower motor lesion is weakness (ultimately paralysis) of affected muscles with marked wasting. The effects of upper motor neurone lesions are more variable, depending on which descending pathways are affected. They are loss of dexterity, weakness and spasticity. An upper motor neurone lesion may cause mild weakness but, nevertheless, be incapacitating because of spasticity and impaired dexterity. On the other hand, a lesion restricted to cells in the primary motor cortex itself causes weakness without spasticity. With upper motor neurone lesions, muscle wasting is much less marked, and occurs late.

Motor system examination

The examination technique for formal assessment of the motor system depends very much on the circumstances. For instance, a follow-up outpatient assessment to gauge the response to treatment of a patient with myasthenia gravis, polymyositis or even chronic idiopathic demyelinating polyneuropathy may be effectively achieved in the consultation room without recourse to the examination couch. Here, it is assumed that the patient is presenting for a diagnosis; this requires complete exposure of limbs, shoulders, trunk and buttocks, and careful assessment of muscle power of a large number of muscles or muscle groups.

Inspection

Start by looking at the muscles and the limbs and trunk. Pathological hypertrophy of muscle is rare. Pseudohypertrophy is also uncommon. It is seen mainly in the calf muscles of individuals with certain muscular dystrophies. It is termed ‘pseudohypertrophy’ because it is associated with weakness, and pathologically there is degeneration of muscle with replacement of muscle tissue by fat.

Wasting of muscle is a common sign of disease, but does not always have a neurological basis. With disuse, muscles atrophy, sometimes quite fast. Generally disuse atrophy is fairly mild. Power is preserved if it can be tested (e.g. quadriceps wasting in someone with severe knee arthritis). Cachexia involves diffuse muscle wasting, but usually power is surprisingly good. Thyrotoxicosis leads to diffuse muscle wasting and ultimately there is weakness (thyrotoxic myopathy). Many myopathic disorders give rise to wasting, and the pattern of wasting (proximal, distal, symmetrical, asymmetrical and selective (e.g. finger flexor muscles in the forearm in inclusion body myositis)) helps diagnostically. Wasting is an important sign of peripheral nerve disease which affects motor nerve fibres. It is denervated muscle which wastes markedly, indicating motor nerve terminal or axon loss. Focal motor nerve demyelination with conduction block but without denervation causes weakness, but there may be little or no wasting. In mononeuropathies, the wasting only affects muscles supplied by the affected nerve. Sometimes an ulnar neuropathy or median nerve lesion at the wrist or a common peroneal nerve lesion can be correctly diagnosed with reasonable confidence just by observing the pattern of wasting. In mononeuropathies, plexopathies and radiculopathies, wasted muscles will be weak. Motor and mixed motor and sensory polyneuropathies also cause wasting, most commonly distally and symmetrically. Disorders of motor nerve cell bodies lead to loss of associated axons and wasting. Thus, a range of pathologies of the spinal cord cause wasting, including processes which just affect motor nerve cell bodies, such as motor neurone disease and hereditary motor neuronopathies (spinal muscular atrophies) and poliomyelitis, and structural spinal cord disorders such as syringomyelia. Many elderly patients appear to have wasting of the small muscles of the hand, but if the strength is normal, there is probably actually no muscle wasting.

Fasciculations are spontaneous contractions of the muscle fibres of individual motor units within a muscle at rest, seen as twitches within a muscle. While widespread fasciculations are rather characteristic of amyotrophic lateral sclerosis, they are not always seen in that condition, and they may be seen in peripheral neuropathies and radiculopathies and in normal individuals who are not fully at rest. They may also be an isolated, benign abnormality.

Pes cavus (Fig. 14.11) with clawing of the toes may be idiopathic or an indication of longstanding imbalance of muscle power in the feet (mainly weakness of intrinsic foot muscles), caused commonly by Charcot-Marie-Tooth disease, but also by other hereditary or congenital disorders of peripheral nerve or spinal cord. Contractures of joints can be a consequence of muscle disease, peripheral neuropathy or CNS disease. Scoliosis is common in neurofibromatosis, but may be a complication of other neurological disorders such as syringomyelia and Friedreich’s ataxia.

Figure 14.11 Pes cavus, with clawing of the toes in a patient with familial neuropathy. This patient had Refsum’s disease and the peripheral nerves were slightly enlarged.

Assessment of muscle tone

Some people can relax their muscles extremely well, whereas others tense up during an examination, sometimes making for difficulty in assessing tone. Generally, in adult neurological practice, apparent hypotonia is not very diagnostically useful. The two common and important forms of pathological increase in muscle tone are spasticity, reflecting an upper motor neurone disorder (imprecisely designated ‘pyramidal’ because the corticospinal tracts constitute the medullary pyramids) and the ‘extrapyramidal’ rigidity of parkinsonism.

Spasticity

Spastic hypertonia in the upper limbs affects flexor muscles more than extensor muscles. This may give rise to a characteristic posture of the limb which is flexed at the elbow, wrist and fingers. There will be more resistance to passive extension of these joints than to passive flexion. The resistance increases in proportion to the speed of stretch of affected muscles, until it suddenly reduces (so-called clasp-knife rigidity). Accordingly, detecting spasticity is best achieved by fairly fast and vigorous movements of the patient’s limb to stretch relevant muscles. Hold the patient’s elbow and hand and extend the elbow briskly, from a fully flexed to a fully extended position. Similar considerations apply at the wrist and fingers. A spastic arm will also have increased tone in pronator muscles. Brisk passive supination of the forearm will elicit clasp-knife rigidity felt as a ‘pronator catch’.

In the leg, spasticity typically affects adductors and extensors more than flexors. With spinal cord lesions, the spasticity is often bilateral (a spastic paraparesis). Mild bilateral adductor spasticity can be detected with the the patient lying supine on a couch or bed. Pick up one leg and abduct it. In doing so, adduction of the contralateral leg will be observed. Mild spasticity in quadriceps can be detected by asking the patient to relax. Then briskly flex his hip by lifting the leg behind the knee. In a normal limb, this will lead to flexion of the knee by gravity of the lower leg. The ankle will remain on the couch, being dragged proximally. If there is spasticity, however, the lower leg will be lifted off the bed briefly before falling back down. Spasticity at the ankle causes plantarflexion. Brisk passive dorsiflexion of the ankle, best done with the knee partially flexed, elicits the spasticity in the form of clonus – a succession of involuntary brief contractions of the calf muscles. Clonus may range from a few beats to sustained clonus in which there are repetitive calf muscle contractions until pressure on the sole of the foot is removed.

Parkinsonian extrapyramidal rigidity

This takes two forms: either an increase in muscle tone affecting any movement of any muscle groups (so-called lead-pipe rigidity); or rigidity which is modified by tremor (so-called cogwheel rigidity, in which a high frequency intermittency in the severity of the resistance to movement is felt). Mild parkinsonian rigidity is sometimes absent when the patient is relaxed, but may be induced by getting the patient to use the arm contralateral to the arm being assessed (activated rigidity). Passive flexion and extension of the wrist is a good manoeuvre to pick up parkinsonian rigidity. Test first with the contralateral arm at rest. Then, if appropriate, test again, this time for activated rigidity, with the patient moving his opposite arm up and down with the fist clenched.

Paratonia (Gegenhalten)

This is seen in patients with fairly advanced dementia. Whichever way you attempt to move the patient’s limb, he puts up active resistance.

Testing muscle power

This is a skill which requires considerable practice, in order to learn how to encourage patients to cooperate fully and demonstrate the full amount of power they have at their disposal, and to be able to make correct judgements about the presence of weakness. With few exceptions, isometric contraction (in which a muscle exerts a force but does not change in length) is tested by the examiner opposing the action of the patient’s muscle(s). Clearly the average healthy young doctor will be stronger than a child or a frail elderly but otherwise normal person, so judgement has to be applied. Conversely some patients will be stronger than the examiner. It is important to be thinking about the patterns of muscle weakness which are likely to be found in different kinds of disease processes; and to look for and register the evolving pattern of weakness as you go along.

A common problem is non-organic weakness. This may reflect malingering or a conversion disorder, but sometimes just indicates that the patient is keen to impress on you that there is something the matter. In non-organic weakness, intermittency of effort is apparent, with variability of power produced from second to second, often with a prominent tendency abruptly to give way or withhold effort. In contrast, the muscle of a patient with organic weakness exerting as much force as he can will give in a smooth, continuous way, not a jerky, fluctuating way. Non-organic paralysis is often quite easy to diagnose because of inconsistencies in the patient’s capabilities. For instance, a patient may walk into the consulting room normally, mount the examination couch unaided but be unable to lift a leg into the air because of apparent paralysis of hip flexion. The non-organic nature of unilateral hip extension weakness may be established by Hoover’s sign. A patient appears to have paralysis of hip extension. Keep a hand under the affected leg and ask the patient to flex the opposite hip against the resistance of your other arm. In doing so, the patient will unwittingly activate the previously paralysed hip extensors.

Clinical methods of recording the severity of muscle weakness have considerable shortcomings, but in neurological practice it is desirable to chart muscle strength in order to document progression or recovery and to gauge the effectiveness of therapeutic interventions. The Medical Research Council scale is widely used (Box 14.3), but a problem with this scale is that the vast majority of muscle weakness one will encounter is grade 4. It also performs badly for fingers and toes where gravity has scarcely any influence, so that grades 1, 2 and 3 are more or less identical. Many clinicians find a scale of normal power, mild, moderate and severe weakness and paralysis is practical for everyday use. Accurate quantitative myometry ought to be a way forward, but has hardly entered routine clinical practice.

Box 14.3 The Medical Research Council scale for grading muscle strength

Grade 0: no contraction

Grade 1: flicker or trace of contraction

Grade 2: active movement with gravity eliminated

Grade 3: active movement against gravity

Grade 4: active movement against gravity and resistance

Grade 5: normal power

Commonly Grade 4 is divided into 4−, 4 and 4+, denoting severe, moderate and mild weakness, and some use 5− to signify minimal weakness.

There is not the space here to describe in detail the testing of all the important individual muscles and muscle groups. Tables 14.6 and 14.7 represent a summary of commonly tested muscles and their actions, but a number of specific points are important:

There are two tests in which muscle strength is routinely tested isotonically (i.e. the muscle shortens while lifting a constant load) as opposed to isometrically. Abdominal trunk muscles are tested by asking the patient to sit up from lying flat with his arms folded on his chest. Standing up from a sitting position or rising from a crouched position are good tests of hip and knee extension and spine extension muscles, and are useful in testing patients with myopathies. Normally these actions can be accomplished without use of the arms. Weak patients often have to resort to using their arms to push themselves up, either using surrounding furniture or, failing that,pushing themselves up with their arms on their own legs (Gowers’ sign; Fig. 14.12).

Testing neck flexion and extension is important in myopathies, in myasthenia gravis and in motor neurone disease.

Deltoids, spinati, the pectoralis major muscles, hip abductors and hip adductors can be tested bilaterally simultaneously, but all other muscles must be tested in each limb separately.

People sometimes test ulnar nerve-supplied small hand muscles by squeezing together the abducted index and small fingers (first dorsal interosseous and abductor digiti minimi muscles). It is better to test these two muscles individually.

Mild weakness of calf muscles (gastrocnemii and soleus) is difficult to detect on a couch. A good technique is to get the patient to walk around on ‘tiptoes’. The ankle sags in a leg affected by mild plantarflexion weakness.

Rather than thinking solely about the myotomes supplying the relevant muscles, it is better simultaneously to be thinking, ‘Is this the pattern of weakness one sees in upper motor neurone disorders (monoparesis, hemiparesis, paraparesis, tetraparesis); is this the weakness of a polyneuropathy (usually distal symmetrical weakness except in demyelinating polyneuropathies which give substantial proximal weakness as well); is the weakness best explained by a nerve root lesion or lesions; is the weakness best explained by a lesion of an individual nerve or by a number of nerves or by a plexus lesion; is the pattern of weakness due to a muscle disorder (often proximal symmetrical weakness)?’

Table 14.6 Muscles of the upper limbs which are commonly examined (P is patient; E is examiner)

Table 14.7 Muscles of the lower limbs which are commonly examined

Figure 14.12 Duchenne muscular dystrophy (Xp21 dystrophy). There is pseudohypertrophy of the weak muscles (e.g. the calves and deltoids). The child is ‘climbing up himself’ with legs widely placed as he gets up from the sitting position to the standing position. This is Gowers’ sign.

Cerebellar system

The anatomy of the cerebellum is complex; it receives afferents of virtually every kind and its efferents connect to virtually every part of the brain and spinal cord. Important afferents include those from the motor cortex, visual cortex, vestibular nuclei and spinal cord. Vestibular afferents connect to the flocculonodular lobe. Lesions here cause disequilibrium and gait ataxia. Spinocerebellar tracts go mainly to the vermis, in the midline of the cerebellum. Lesions here cause truncal and gait ataxia. Each cerebellar hemisphere receives a major input from the contralateral cerebral cortex via pontine nuclei and the middle cerebellar peduncles. The major output from the cerebellum is via the superior cerebellar peduncles. Fibres from the cerebellar hemispheres cross to the contralateral red nucleus and thalamus, thence to spinal cord and basal ganglia and cerebral hemispheres. Thus, whereas cerebral cortex lesions affect contralateral limbs, cerebellar hemisphere lesions cause incoordination of ipsilateral limbs.

Incoordination, ataxia and tremor are the main effects of cerebellar lesions. Given the widespread afferent and efferent connections of the cerebellum, it is clear that lesions outside the cerebellum itself may have clinical manifestations which closely resemble those of cerebellar disease, and this needs to be borne in mind when examining patients. Thus, gait ataxia may be seen with cerebral, brainstem or spinal cord disorders, and tremor and ataxia can be manifestations of brainstem lesions.

Examination of limb coordination

The finger–nose test

A mild cerebellar lesion gives rise to no limb signs at rest, but movements of affected limbs may be accompanied by action tremor. Actions are clumsy and inaccurate. Coordination of the arm is tested by the finger–nose test. Hold up an index finger in front of the patient. Ask him to touch it with the tip of his index finger, then with the same finger to touch his nose, and then ask him to carry on, touching alternately your finger and his nose. Some make the test a bit more difficult by moving the finger from place to place, but this adds little. More important is to make sure that the patient has to stretch a little to reach the finger, so that coordination is seen over the full range of movement of the arm. The observed action tremor is of fairly low tremor frequency, sometimes of quite large amplitude, and it becomes more marked in amplitude as the patient’s finger approaches the target (his nose or your finger). This gives rise to the term ‘intention tremor’.

In more severe cerebellar lesions, there will be postural as well as action tremor. In the extreme, the postural and action tremor are incapacitating. In such circumstances, the finger–nose test is inappropriate, being dangerous to the patient, whose finger might poke an eye or any other part of his face.

Dysdiadochokinesis

Ask the patient to tap his fingers rapidly on the back of his other hand. Then get him to repeat the test, this time turning the tapping hand so that the tapping is alternately done with the palmar and the dorsal sides of the fingers. Each tap should be on the same spot, not adjacent parts of the back of the hand.

Irregularity and clumsiness indicate an ipsilateral cerebellar hemisphere disturbance. Dysdiadochokinesis is not very specific; impairment is also seen in pyramidal and extrapyramidal disorders as well.

The heel–shin test

This tests lower limb coordination. The patient lies on a couch or bed. Ask him first to lift one leg into the air; then to put the heel of that leg onto the shin of the other leg just below the knee and run the heel down the front of the shin onto the dorsum of the foot. Cerebellar dysfunction is revealed as tremor when the patient attempts to place his heel at the top of the shin, and as an inability accurately to run the heel down the shin.

In testing cerebellar function, allowance has to be made for any weakness, particularly spastic weakness which by itself causes a certain amount of incoordination. Furthermore, it is essential to test proprioception, because proprioceptive loss can give rise to signs which look just like cerebellar incoordination (sensory ataxia).

Reflexes

The tendon reflex, abdominal reflexes and plantar reflexes comprise the major commonly tested reflexes.

The tendon reflexes

The tendon reflexes are monosynaptic stretch reflexes. Sudden stretching of a muscle by striking its tendon sends an impulse from muscle spindle afferents which synapse directly with motor neurones, leading to reflex contraction of that muscle. The tendon reflexes provide information about both the motor system and the sensory system. Abnormally brisk tendon reflexes contribute to the clinical picture of an upper motor neurone disorder. Absence of reflexes occurs in disorders of sensory afferents from muscle spindles, in a wide range of sensory polyneuropathies, radiculopathies and mononeuropathies. Motor neuropathies and eventually myopathies may entail areflexia, but areflexia more commonly reflects a sensory rather than a motor system disorder. The other important cause of widespread areflexia, which can cause considerable confusion, is a spinal cord lesion which is extensive up and down the cord. In this situation, interruption of afferents to motor neurones in the anterior horns, or damage to the motor neurones themselves, prevent the reflexes from occurring. Examples include syringomyelia, extensive myelitis, spinal cord infarction and extensive intramedullary spinal cord tumours.

Pathologically brisk reflexes below a particular myotome level raise the possibility of a spinal cord lesion between the lowest normal reflex level and the highest abnormal reflex level. Remember that a focal spinal cord lesion will interrupt the pathway of any reflex at that level. Thus, the combination of loss of a reflex at a particular level and abnormally brisk reflexes subserved by levels below points strongly to a focal spinal cord lesion. One of the limitations of these analyses is the restricted number of reflexes that can be examined. The biceps reflex is at C5 or C6 level and there is no reflex that corresponds to C4 or higher except for the jaw jerk. If all the reflexes are pathologically brisk but the jaw jerk is not, there may be a high cervical spinal cord lesion. Normal upper-limb power and reflexes and a spastic paraparesis with pathologically brisk lower-limb reflexes may indicate a thoracic spinal cord lesion, but there are no tendon reflexes between C8 (finger reflexes) and adductor reflexes (L2 or L3) to localize the lesion more precisely.

Testing the tendon reflexes

Eliciting tendon reflexes is not completely straightforward and requires practice. The aim is to ensure that the tendon of the relevant muscle being tested is briskly and effectively struck. Accordingly, sufficient force must be delivered. For the biceps reflex, place your own finger over the tendon and strike your finger. Similarly the brachioradialis reflex can be elicited by applying the tendon hammer to your own fingers positioned just above the wrist on the lateral aspect of the radius bone. The other standard reflexes (triceps, knee (quadriceps) and ankle (gastrocnemii and soleus)) involve directly striking the tendon with the tendon hammer. The standard tendon reflexes examined are summarized in Table 14.8.

Table 14.8 Frequently examined tendon reflexes

The range of briskness of normal reflexes is very variable both between and within individuals, so it is important not to jump to conclusions about the presence of upper motor neurone lesions or polyneuropathies just on the basis of reflexes alone. Normal individuals who have absent reflexes tested in the standard way will usually have reflexes if they are brought out by reinforcement. To reinforce lower limb reflexes, ask the patient to put his hands together with the fingers interlocked. Then get ready to elicit the reflex, ask the patient to squeeze with his hands and then directly test the reflex. Upper limb reflexes can also be reinforced. Ask the patient to squeeze firmly something held in the hand contralateral to the limb in which the reflexes are to be tested (e.g. the barrel of a standard ophthalmoscope).

Abdominal reflexes

The stimulus is a light stroke of the abdominal skin using an orange stick. The normal response is contraction of abdominal wall muscles in the region where the stimulus is delivered, noted as movement of the umbilicus towards the region where the response is positive. The reflex is absent in spinal lesions above the level at which the reflex is being tested and the reflexes are sometimes absent at a very early stage in multiple sclerosis. With symptoms or signs of a sensory level on the abdomen, the reflexes may be absent below the sensory level, retained above.

Testing the abdominal reflexes

The patient should be supine, relaxed, with the abdomen fully exposed. Start the stroke of the orange stick right round in the flank, drawing it to the midline. Test all four quadrants of the abdomen.

The plantar reflex

The normal response to uncomfortable or painful cutaneous stimulation of the sole of the foot includes flexion of the toes. A remarkably reliable feature of an upper motor neurone lesion (anywhere in the spinal cord above L5 or in the brain), affecting the leg being tested, is the extensor plantar response. The minimum extensor response is extension of the great toe only. In addition there may be fanning of the other toes, and a very strong response in a paralysed patient comprises dorsiflexion of the ankle, flexion of the knee and flexion of the hip. If you are dealing with a patient who clearly has spasticity of the leg, a pyramidal distribution of weakness, pathologically brisk reflexes and ankle clonus, it hardly matters what the plantar response is. Occasionally, however, a patient has weakness without spasticity or hyperreflexia and the evidence that it is a CNS disorder hinges on the plantar reflex. Conversely, agitated individuals may have increased tone and very brisk reflexes but the plantar reflex responses reassure one that there is no neurological problem.

A patient with lower motor neurone paralysis of toe extension cannot have a conventional extensor response regardless of the severity of any upper motor neurone disorder he may also have. A small number of malingerers learn to produce extensor responses.

Testing the plantar reflex

The ideal instrument to use is an orange stick (Fig. 14.13). Hold the patient’s foot. Apply the orange stick to the sole of the foot on the lateral border just in front of the heel. Draw it forward towards the base of the fifth toe. This may suffice. Some continue round across the ball of the foot. It is best to press fairly firmly, warning the patient that this is not a pleasant test. Try to do the test effectively once or twice, not a large number of times. If you remain in doubt as to whether a patient’s response is extensor or not, then later, when testing pinprick sensation, test the dorsum of the toe in question. Involuntary extension of the toe towards the pin is an extensor response.

Figure 14.13 The plantar response. A firm, stroking stimulus to the outer edge of the sole of the foot evokes dorsiflexion (extension) of the large toe and fanning of the other toes.

Movement disorders

This is a large field encompassing a whole range of abnormalities of posture, locomotor function and movement, with a spectrum from the very common to the distinctly rare. Both hypokinesia and hyperkinesia are abnormal, and the most common important disease in this sphere, Parkinson’s disease, combines both, with akinesia, bradykinesia, dystonia, tremor and dyskinesia (the latter usually drug induced).

Tremor

Tremor by itself is a common reason for neurological referral. Tremor that has not hitherto been noticed by the patient or his doctors may contribute to neurological diagnosis. Getting a tremor diagnosis wrong is rarely serious, but giving patients incorrect diagnoses or prognoses is unsatisfactory and may lead to futile and inappropriate treatments, or deprive a patient of worthwhile treatment.

The common tremor disorders include enhanced physiological tremor, essential tremor, parkinsonian tremor, dystonic tremor, cerebellar (‘intention’) tremor, drug-induced tremor and psychogenic tremor (Table 14.9). Combinations of tremor and myoclonus are seen in encephalopathies, mainly in hospitalized patients.

Table 14.9 Common forms of tremor

Tremor variety	Comment
Physiological	Normal

Enhanced physiological

Normal in a stressful enough situation

A constitutionally anxious person may have this and psychogenic tremor

Thyrotoxicosis

Perhaps a variant of enhanced physiological tremor

Drug induced

The mechanisms here are various: some drugs may also cause ataxia, some parkinsonism, some polyneuropathy

Essential

Sporadic or familial

Called benign, but severe cases are disabling

Mainly upper limbs, but severe cases can affect legs too (see text)

Parkinsonism

Mainly idiopathic Parkinson’s disease (see text), but sometimes parkinsonian tremor is seen in other forms of parkinsonism

Wilson’s disease must be excluded in young people with tremor

Dystonic

More jerky and irregular than essential tremor, particularly with jerks occurring in one direction

Features of dystonia are also seen

Often a neck tremor

Cerebellar

See text

In association with polyneuropathy

Some patients with Charcot-Marie-Tooth disease

Some patients with chronic idiopathic demyelinating polyneuropathy

Psychogenic

Typically exaggerated in clinic

Variable

Settles when patient distracted from shaking

Patient cannot maintain the same frequency of tremor when performing a repetitive task with the contralateral limb at a different frequency unless it is a harmonic

The classical tremor of Parkinson’s disease (PD) is called a rest tremor (a slight contradiction in terms), and it is not always easy to diagnose. The patient’s limb shakes when it is relaxed and doing nothing. Getting a patient into a position which allows his arms completely to relax in a chair may be difficult; beware you are not simply observing the postural tremor of a patient with essential tremor. In fact, you can quite often establish the presence of rest tremor as well from the history as from examination: ‘When relaxed on a comfortable sofa watching television, does your arm start to shake?’, ‘Do any of your limbs shake when you are lying in bed?’ Rest tremor may be observed in a relaxed patient sitting in a chair or lying on a couch. Furthermore, if a patient is walking and the fingers of one hand are shaking (and the arm is not swinging), it is likely to be the rest tremor of PD. PD tremor is seen most commonly in the fingers, wrist and forearm. It may also affect a foot. Classically, when a PD patient with upper limb rest tremor holds his hands out in front of him, his tremor stops for 10-20 seconds, whereafter a postural tremor may become evident. PD tremor is almost invariably asymmetric, starting in one limb and remaining more marked on that side throughout.

Essential tremor is not present at rest. It is noted with maintained postures and during movement. It mainly affects upper limbs. It is usually not markedly asymmetric. The action tremor may be examined during the finger–nose test and may also be assessed by tasks such as drawing a spiral, or a wavy line between two straight lines, or while writing, and these can be documented in case records. Jaw and lip tremor can be seen in PD and essential tremor patients.

Even with all the other aspects of examination at one’s disposal (rigidity, bradykinesia/akinesia, posture, gait), distinguishing PD and essential tremor is sometimes difficult. Where there is uncertainty, withholding judgement and reviewing after an interval is often helpful.

Parkinson’s disease

The main features of PD are summarized in Box 14.4. Rigidity and tremor have been discussed above. Posture and gait are discussed below.

Box 14.4 Cardinal features of Parkinson’s disease

Tremor

Akinesia, bradykinesia

Rigidity

Abnormalities of posture

Impairment of postural control and balance

Abnormalities of gait

Dysphonia, dysarthria, stammer

Impaired facial expression and generalized bradykinesia or akinesia are observations, but bradykinesia can also be tested formally, elements of the Unified Parkinson’s Disease Rating Scale being readily incorporated into routine clinical practice (see Box 14.5). Postural stability is tested by the pull test, done after testing gait.

Box 14.5 Tests for bradykinesia in Parkinson’s disease

1 Finger tapping:

– ask the patient to tap repeatedly with his index finger on his thumb. The amplitude of each movement should be as large as possible and the speed should be as fast as possible. Test one side, then the other, not both together

2 Hand movements:

– ask the patient repeatedly to fully open his fist and fully close it, again with maximum amplitude and speed. Test one side, then the other, not both together

In these two tests, in PD there is slowness and progressive reduction of amplitude of the movement, sometimes such that the movement ceases altogether. Asymmetry is the rule.

3 Pronation-supination movements of the arms:

– ask the patient to hold both arms out, and repeatedly to pronate and supinate them, with maximum amplitude and speed. Test both arms together.

In this test, asymmetry with impaired amplitude on the more affected side is readily observed.

4 Leg agility:

– ask the patient to stamp his heel rapidly and repeatedly on the ground, lifting his whole leg at least 3 inches (8 cm) each time. Test each leg separately.

The pull test

The patient stands with his feet side by side. Stand behind the patient with one foot slightly behind the other. Explain that, without warning, you are going to pull the patient abruptly backwards by his shoulders. The patient’s task is not to fall over. He is allowed to step backwards in order to maintain his balance. Be prepared to catch the patient, should he topple. A normal individual either remains upright even without moving his feet, or does so by taking a single step backwards. ‘Retropulsion’ refers to the patient taking a number of small paces backwards, either succeeding or failing to reposition his centre of gravity; this is parkinsonian and abnormal. Some patients will simply fall backwards without taking any paces at all.

Other movement disorders (hyperkinetic movement disorders)

Generally these disorders are identified simply by history and by observation rather than any other component of examination. They are summarized in Table 14.10.

Table 14.10 Common kinds of movement disorder

Movement disorder	Characteristics
Parkinsonism	See text
Dystonia	Abnormal muscle contractions which may be sustained or repetitive, also involving co-contraction of antagonist muscles, leading to an abnormal posture, with or without jerks or tremor Associated pain and disability Can be focal, segmental, axial or generalized A wide range of causes In adults, idiopathic cervical dystonia is common

Chorea and athetosis (choreoathetosis)

Chorea denotes irregular, brief, jerky, unrepetitive, unintentional movements, affecting differing parts randomly (unilateral in hemichorea)

In mild cases, the patient just looks fidgety

Many causes including metabolic, drug induced, autoimmune, neurodegenerative

Athetosis denotes slower, more writhing movements than chorea

The two often coexist, particularly in levodopa-induced dyskinesia

Ballism

Not very common

Usually hemiballism, due to an ischaemic stroke affecting the subthalamic nucleus

The movements are violent with flinging of the limbs

Myoclonus

Sudden shock-like jerks of limbs or trunk

Can reflect cortical, brainstem or rarely spinal cord pathology or an encephalopathy

Epileptic myoclonus is fairly common

Asterixis

Negative myoclonus. A sudden brief loss of tone. Particularly associated with hepatic encephalopathy

Tardive dyskinesia

A complication of dopamine antagonist neuroleptic medication

Abnormal movements may affect any body part, but usually mainly affect the face, lips, jaw and tongue

Tic

Usually fairly small twitchy movements made semivoluntarily by a patient

Preceding urge to make the movement, and brief relief having done so

Often affect the face (blinks, grimaces, twitches of the nose), neck, shoulders

An individual may have one or several different tics

Sensation

The cell bodies of primary sensory neurones are in dorsal root ganglia and equivalent ganglia on cranial nerves (particularly the trigeminal ganglion). Their peripheral axons convey sensory information from sensory end organs in skin, muscle spindles and tendons. Their central axons project into the spinal cord or brainstem. Large diameter myelinated axons transmit proprioception, vibration and touch. Small diameter myelinated and unmyelinated axons transmit pain and temperature. The centrally projecting axons for proprioception and vibration sense enter the spinal cord and turn immediately to head rostrally in the posterior (dorsal) columns ipsilaterally, to synapse in the gracile and cuneate nuclei at the cervicomedullary junction. Axons from these nuclei cross in the medulla and proceed to the thalamus. In contrast, axons for pain and temperature, having entered the spinal cord, synapse in the dorsal horns. The axons of second-order sensory neurones cross over to the contralateral anteriorly (ventrally) situated spinothalamic tracts and run rostrally all the way to the thalamus. Touch sensation travels by both routes. Sensory pathways from the trigeminal sensory nuclei cross in the brainstem to project to the contralateral thalamus. From the thalamus, third-order neurones project via the posterior limb of the internal capsule to the primary sensory cortex in the parietal lobe, which is somatotopically organized (Fig. 14.14), akin to the primary motor cortex.

Figure 14.14 Somatotopic representation in the primary sensory cortex.

The anatomical separation of different modalities of sensation in the spinal cord accounts for dissociation of sensory loss in spinal cord lesions which affect one side of the spinal cord or which affect either the anterior or posterior cord (see below).

Cutaneous sensory examination

By the time sensation is examined, it may be apparent from the history and the clinical examination thus far what the diagnosis is and, consequently, what needs to be looked for during sensory testing. This is important because, in general, sensory testing needs to be goal directed; otherwise it tends to be fruitless or misleading. If a patient gives a very clear description of impaired sensation in the distribution of, for example, the ulnar nerve, diagnostically it makes little difference whether he can or cannot feel sharp pinpricks in the area of his symptoms. The symptoms still suggest an ulnar neuropathy either way. With very few exceptions (the corneal reflex would be one), all sensory tests are subjective – in other words, the examiner relies on what the patient reports. Patients with no sensory symptoms may have signs of impaired cutaneous sensation; in that situation, the examiner has to exercise judgement as to whether they are of significance.

Disorganized sensory testing tends to confuse both patient and examiner. With cutaneous sensory testing, the goal is to see whether any hypoaesthesia conforms to a meaningful pattern (see Table 14.13 and Figs 14.15 and 14.16). Defining an area of hypoaesthesia is almost invariably better achieved by starting testing within the area of hypoaesthesia and moving the stimulus out into areas where sensation is normally perceived.

Figure 14.15 Anterior view to show the segmental innervation of the skin (left) and the peripheral nerve supply (right).

Figure 14.16 Posterior view to show the segmental innervation of the skin (left) and the peripheral nerve supply (right).

One of the less satisfactory modalities of sensation to test is light touch. It is often done by dabbing the skin lightly with a piece of cotton wool, but there may be differences between touching the skin and stroking it. Tickle is a different modality; moving hairs on hairy skin is different again. In the context of spinal cord pathology, an abnormality of light touch sensation will not differentiate a posterior column lesion from one affecting the spinothalamic tracts. When testing light touch sensation, it can be helpful to ask the patient to close his eyes and then to report when he perceives the touches; some patients with anaesthesia will report that they feel touches when they see them being applied. Touch/pressure can be somewhat more rigorously assessed using a 10-gram monofilament to apply a standard quantity of pressure, and this can be useful as a screening test in situations where a patient is at risk of development of sensory peripheral neuropathy (e.g. diabetes).

Pinprick testing is more informative diagnostically and useful in mononeuropathies, polyneuropathies, radiculopathies and spinal cord lesions as well as brainstem and cerebral hemisphere lesions. It is, however, totally subjective. The patient reports whether the pinprick has a sharp, slightly painful quality or whether it is merely felt as a blunt touch. Testing can be done with the patient looking. In some clinical situations, it is worth testing pinprick sensation even when a patient has no symptoms. A patient with a spastic monoparesis of one leg could have a brain or spinal cord lesion, but impaired pinprick sensation in the contralateral leg would strongly suggest a spinal cord lesion (Brown-Séquard lesion, see below). A patient with a slowly progressive spastic paraparesis or tetraparesis might have a degenerative disorder, but the finding of a clear-cut sensory level on the trunk or neck would strongly suggest a structural spinal cord lesion.

Perception of heat and cold can be tested but in routine clinical practice adds little. A patient with impaired thermal sensation caused by a cerebral or spinal cord disorder will have impaired pinprick sensation in the same distribution. Impaired thermal sensation in patients with small fibre polyneuropathies is best assessed in a neurophysiology laboratory.

Vibration sense

Patients do not complain of impaired vibration sense, but its finding on examination is a useful sign of either a polyneuropathy or a spinal cord lesion. Vibration sensation is conveyed in large diameter sensory neurones, the central projections of which run in the posterior columns of the spinal cord.

Testing vibration sense

Set a low-frequency tuning fork vibrating noiselessly by striking it against the heel of your hand. Then apply the base of the tuning fork to bony parts of the limbs and ask the patient to report whether he feels the vibrations. Start distally and work proximally if necessary. In the upper limb, start on a distal phalanx. If the patient has absence of vibration sense there, then test the wrist and, if necessary, the elbow. In the lower limb, test the distal phalanx of the big toe, and then the medial malleolus and top of the tibia, if necessary. If you suspect you are getting false positive answers from the patient, ask him to close his eyes and then randomly apply the tuning fork either vibrating or not vibrating to his limb; the patient reports whether it is or is not vibrating.

Proprioception

Impaired proprioception occurs in large fibre sensory (or sensory and motor) polyneuropathies, spinal cord lesions affecting the posterior columns and in lesions at higher levels including lesions of the sensory cortex. Proprioceptive loss is the basis of sensory ataxia. Patients with polyneuropathies which cause severe proprioceptive loss have gait and limb ataxia which looks very like cerebellar ataxia. There are several clinical tests or signs which address proprioception: joint position sense (more strictly joint movement sense), pseudoathetosis and Romberg’s test.

Testing joint position sense

Joint position testing does require the patient to look away or have his eyes closed. With the thumb and index finger of one hand, hold each side of the middle phalanx of the patient’s middle finger. With your other hand, grasp the sides of the distal phalanx. Explain to the patient that he is to say which way his finger moves, and that it will only go up or down and that the movements up or down will be random. Move the distal phalanx either up or down through a small angle – the patient should be able to perceive as small a movement as you will be able to make. Make sure each movement is random, not just up, down, up, down, etc. If the patient fails to understand the test or to concentrate, do it first with him looking at the joint being tested. If joint position sense is impaired at the distal interphalangeal joint, move more proximally to the metacarpophalangeal joint and, if necessary, to the wrist or elbow, employing bigger angles of movement. The same applies in the foot and leg: start with the interphalangeal joint of the big toe and, if necessary, the ankle or knee. The normal threshold for perception of joint movement in the toe is larger than in the finger.

Pseudoathetosis

Patients with impaired joint position sense in their fingers may exhibit so-called pseudoathetosis: outstretched fingers drift up or down or to the side when the patient has his eyes closed. This is because, proprioception having failed, vision is the only means by which the patient knows where his fingers are and can keep them in one place (Fig. 14.17).

Figure 14.17 Paraneoplastic sensory neuropathy due to small cell carcinoma of the lung. With the eyes closed, the patient’s outstretched arms become flexed and abnormal postures develop in the fingers.

Romberg’s test

Ask the patient to stand with his feet side by side. Having established that his balance is satisfactory with his eyes open, ask him to close his eyes, having reassured him that nothing untoward will happen. If he loses balance with his eyes closed, the test is positive. You need to be prepared to catch the patient if he shows signs of toppling. Sometimes this kind of proprioceptive loss is evident in the clinical history – the patient comments on loss of balance in the dark, or when he closes his eyes to wash his face.

Cortical sensory loss

Cerebral hemisphere lesions may disrupt sensory afferents or the primary sensory cortex in such a way as to give rise to very straightforward sensory loss affecting the usually tested modalities. In the same way that occipital lesions may give rise either to visual loss or to disorders of visual interpretation, parietal lesions can cause sensory impairment without anaesthesia. One such disorder is sensory inattention which is akin to visual inattention. A patient may feel sensory stimuli in limbs on the affected side, so does not have a hemianaesthesia, but sensory stimuli presented simultaneously on both sides are registered by the patient only on the normal side.

In tactile agnosia, a patient has no difficulty naming an item shown to him, but with his eyes closed and the item put into his hand, he is unable to work out by its size, consistency and texture what it is. Similarly a patient may be unable to distinguish different very familiar coins by feel alone. Dysgraphaesthesia is another form of cortical sensory impairment. Use an orange stick or a pen with the cap on. Write numbers on the patient’s palm, clarifying with him which way up they are going to be. With eyes open, the patient will cope with 2, 3, 6, 1, etc., but will not recognize the numbers with his eyes closed.

Clearly it is only valid to test these sorts of cortical sensory impairments in patients who do not have a hemianaesthesia.

Testing sensory inattention

This is done with the patient’s eyes closed. Randomly touch lightly his right or left hand (or foot) or both together, getting him to report each time whether he feels the touch on the right or left or on both sides. A patient who has right-left disorientation can still do this test, indicating which side or sides were touched by a finger movement. The lesion responsible for sensory inattention may be in the parietal cortex or in the subcortical white matter.

Posture and gait

In the outpatient setting, a patient’s gait will inevitably be observed, although it may well be desirable to inspect it in some detail, perhaps by taking him out into a corridor. In hospitalized patients, it is easy to neglect to test gait if the patient is encountered in his bed. Mobility is so fundamental that gait must be considered and assessed in every appropriate patient and does not take long to do.

First, simply observe the patient standing. Look for abnormalities of posture. Established PD gives a kyphotic posture (Fig. 14.18). Neck extension weakness causes forward flexion of the neck; in extreme cases, a state of drop head is apparent. Axial dystonia may be observed. Muscular dystrophy may be associated with hyperlordosis. Check the patient’s balance and do Romberg’s test (see above). Then ask the patient to walk a short distance, turn round and walk back again. Mild gait ataxia can be brought out by getting the patient to walk heel to toe. If relevant, test for retropulsion (the pull test; see p. 312).

Figure 14.18 Parkinson’s disease, showing the typical rigid, flexed posture involving the trunk and limbs. The face is impassive.

Table 14.11 provides a summary of important kinds of neurological gait disorders. Sometimes it can be difficult to be certain that a patient with a frontal gait disorder does not also have PD. Patients with severe osteoarthritis of the hips sometimes have a gait disorder which looks deceptively like a myopathic gait. Finally, as in other domains, a functional gait disorder does not necessarily mean that there is no organic disease.

Table 14.11 Common gait disorders

Gait	Characteristics
Myopathic (proximal, symmetrical myopathy)	Hyperlordosis (axial and pelvic muscle weakness) Waddling gait (weak gluteus medius muscles, among others, bilaterally)

High stepping or ‘steppage’

A consequence of foot drop (unilateral or bilateral) – common peroneal nerve lesion, motor polyneuropathy, e.g. Charcot-Marie-Tooth disease, distal myopathy

The leg has to be lifted abnormally high to make a step

With mild ankle dorsiflexion weakness, the foot slaps onto the ground as weight is transferred onto the heel

Ataxic

Midline cerebellar lesion (cerebellar vermis): wide-based unsteady gait with irregular sized paces and potential to topple in any direction; there may be little or no limb incoordination

Cerebellar hemisphere lesion: the patient veers towards the side of the lesion; there is ipsilateral limb incoordination

Sensory ataxia: there may be limb and gait incoordination

Hemiparetic

The spastic arm is held adducted at the shoulder with the elbow flexed and the forearm in front of the chest with flexion at the wrist and fingers

Swinging of the affected arm is reduced

The spastic leg is stiff with impaired knee flexion and ankle dorsiflexion, with abduction of the leg to bring the plantarflexed foot round and forward when taking a step (circumduction)

Spastic (paraparesis; tetraparesis)

Bilateral spastic legs

Bilateral circumduction, such that the leading leg may end up adducted in front of the trailing leg – hence a ‘scissor gait’

Parkinsonian

Kyphotic posture

Start hesitation

Initially small paces, which may get bigger

Acceleration of rate of steps once walking initiated (‘festinant gait’)

Reduced or absent arm swing unilaterally or bilaterally

May suddenly get stuck, e.g. in a doorway

Increased number of paces to turn round

Improvement of gait with visual cues on the ground

Frontal gait disorder
This term has a number of mainly less satisfactory synonyms, including gait apraxia, lower body parkinsonism, atherosclerotic or vascular parkinsonism, marche à petits pas

Gait ignition failure

Start hesitation

Small paces (but no acceleration)

Unsteadiness

Improvement of gait with visual cues on the ground

Prominent swinging of the arms

Ability to use the legs to make cycling movements on a bed or in a chair, yet inability to use legs to walk

Patterns of motor and sensory signs

Formulating the nature of the neurological problem and its localisation on the basis of the signs requires a combination of basic anatomical knowledge and pattern recognition. It is important to be able to recognize the limitations of information the physical signs convey in terms of localization. A patient with gait ataxia and extensor plantar reflexes, and no other signs, could have a lesion in the thoracic or cervical spinal cord or in the cerebellum with early brainstem compression, or it could be a diffuse cerebral process such as small vessel cerebrovascular disease or hydrocephalus. It may also be that two different lesions account for the two manifestations. Conversely, dysfunction affecting several different systems does not necessarily imply a multifocal disorder: diplopia, nystagmus, dysarthria, ataxia, upper motor neurone signs in the limbs, widespread sensory loss and impairment of bladder control might be caused by multiple sclerosis, but a single brainstem lesion could equally account for all of the symptoms and signs.

In the following section, patterns of motor signs and patterns of sensory signs are outlined separately – and, of course, the examiner encounters them sequentially, but for many syndromes it is the characteristic combination of motor and sensory features that allows accurate diagnosis.

Patterns of motor signs

Diagnosing lesions of individual motor or motor and sensory peripheral nerves requires knowledge of which muscles are supplied by which nerve; the same considerations apply to nerve root lesions. Plexus lesions can be difficult, particularly if patchy and multifocal, but can sometimes be diagnosed confidently on clinical grounds simply from the anatomy. For example, a patient with a combination of what appears to be a radial nerve lesion and an axillary nerve lesion will have a lesion affecting the posterior cord of the brachial plexus.

Distal symmetrical weakness in the limbs would be typical for a generalized motor polyneuropathy. The same pattern can be seen in distal myopathies and some spinal muscular atrophies (hereditary motor neuronopathies), neither being common.

Demyelinating polyneuropathies (Guillain-Barré syndrome (GBS) being the most important) give rise to proximal as well as distal weakness, short nerves being as susceptible to conduction block as long ones. Hence, the presentation of GBS may be with exclusively ‘proximal’ and life-threatening weakness of muscles of swallowing and breathing.

Mainly proximal, symmetrical limb weakness should prompt consideration of myopathy, particularly polymyositis and dermatomyositis, and muscle disease secondary to metabolic or drug-induced disorders such as steroid myopathy, thyrotoxic myopathy and osteomalacic myopathy. Test getting out of a chair or rising from a crouch. The different muscular dystrophies tend to have particular patterns of muscle involvement which may help diagnostically.

Patients who have weakness and no sensory symptoms or signs and no upper motor neurone signs usually have muscle disorders or neuromuscular junction disorders, (such as myasthenia gravis (MG), Lambert Eaton myasthenic syndrome or botulism). Typically, MG affects the eyelids, eye muscles, face, jaw, muscles of swallowing and breathing and axial and proximal limb muscles, but atypical cases occur.

Upper motor neurone disorders affecting the leg

The lesion may be in the spinal cord or brain. Weakness affects the flexor muscles more than extensor muscles; hence the abnormal findings are of weakness in hip flexion (iliopsoas), knee flexion (hamstrings) and ankle dorsiflexion (tibialis anterior). Spasticity usually predominates in the hip adductors and the extensor muscles of the leg and foot (gluteus maximus, quadriceps and calf muscles). These circumstances account for the characteristics of the hemiparetic and paraparetic gait (see Table 14.11).

Upper motor neurone disorders affecting the arm and hand

Here the typical pattern is almost the opposite of that in the leg: weakness mainly affects deltoid and the extensors of the arm and hand – elbow extension (triceps), wrist extensors and finger extensors. Spasticity is mainly in the flexors (biceps and brachialis, wrist flexors and finger flexors) and in forearm pronators. Thus, the typical posture of the arm in an ambulant patient with a hemiparesis is adduction at the shoulder, flexion at the elbow, pronation of the forearm and flexion of the wrist and fingers.

The distribution of weakness in upper motor neurone lesions of the limbs is often referred to as ‘pyramidal’, a useful but not completely accurate term. Table 14.12 summarizes where in the CNS lesions need to be to produce the various categories of upper motor neurone lesions.

Table 14.12 Localization of upper motor neurone lesions

Pattern of weakness	Site of lesion
Spastic monoparesis	Cerebral hemisphere Arm (and face) – MCA territory Leg – ACA territory Brown-Séquard syndrome in thoracic cord gives a monoparesis of the ipsilateral leg

Spastic paraparesis

Thoracic spinal cord lesion (i.e. above lumbar cord, but below cervical cord)

A parasagittal meningioma in the falx between the cerebral hemispheres affecting the motor cortex for the leg bilaterally is a much quoted but rare cause of a paraparesis

Spastic hemiparesis

A large hemisphere lesion, e.g. MCA territory stroke, but the arm will be worse affected than the leg

A lesion of the internal capsule

Pure motor hemiplegia is a lacunar syndrome

A brainstem lesion affecting the corticospinal tract on one side

Brown-Séquard syndrome in the high cervical spinal cord

Spastic tetraparesis

High cervical spinal cord lesion, e.g. C3/C4 disc

Diffuse bilateral cerebral hemisphere disease affecting motor pathways bilaterally, e.g. small vessel cerebrovascular disease

Hydrocephalus

Brainstem disease affecting the corticospinal tracts bilaterally, e.g. basilar artery territory stroke (which causes locked-in syndrome)

‘Cortical hand’

A small lesion in the primary motor cortex subserving the hand

Weakness and difficulty using the hand but little or no spasticity

‘Cortical foot’

A small lesion in the primary motor cortex subserving the foot

Weakness and difficulty using the foot but little or no spasticity

ACA, anterior cerebral artery; MCA, middle cerebral artery.

Patterns of sensory loss (Table 14.13)

The diagnosis of lesions of individual sensory peripheral nerves or the sensory component of mixed nerves requires knowledge of anatomy, in this case the area of cutaneous sensation mediated by the nerve in question (see Table 14.13 and Figs 14.15 and 14.16). In lesions affecting mixed nerves, sensory symptoms with or without signs commonly precede motor symptoms and signs. Thus, a clear description by a patient of sensory loss in ulnar nerve distribution provides compelling evidence for an ulnar neuropathy even if there are no signs. The right combination of motor and sensory signs allows the diagnosis of a mononeuropathy to be made. Nerve conduction studies and electromyography may contribute to the assessment of the nature of the lesion (precise location, extent of conduction block, extent of axonal damage, subclinical involvement of other nerves, presence of an underlying subclinical polyneuropathy) but is not necessary for making the diagnosis if there are clear-cut signs.

Table 14.13 Patterns of sensory loss

Clinical sensory findings	Site of lesion
Hemianaesthesia (all modalities) Incomplete, e.g. face and arm Complete	Parietal cortex or subcortical white matter (corona radiata) Thalamus or internal capsule Pure sensory stroke is a lacunar syndrome

Crossed sensory deficit: loss of cutaneous sensation on one side of the face and loss of spinothalamic tract-mediated sensation on the other side of the body

Lateral medullary syndrome: lesion of spinal tract and nucleus of trigeminal ipsilateral to the facial sensory loss, and of crossed spinothalamic tract

Cape or half-cape distribution of dissociated suspended sensory loss (spinothalamic, with an upper and a lower level) with preserved proprioception and vibration sense

Central cord lesion: syringomyelia (and syringobulbia if there is no upper level but the sensory loss affects the face)

Loss of all modalities below a dermatomal level on legs (rare), trunk or neck

Transverse spinal cord lesion affecting posterior columns and spinothalamic tracts

Cord compression by tumour, cord trauma, severe myelitis

As above but with sacral sparing of cutaneous sensory loss

A severe intramedullary spinal cord lesion, e.g. tumour, bleed, but with sparing of the outermost spinothalamic fibres which come from sacral dermatomes

Brown–Séquard syndrome: loss of spinothalamic sensation on one side, with a level, and loss of vibration and proprioception in affected limbs on the other side

Hemisection of the spinal cord: involvement of the posterior columns (uncrossed) and spinothalamic tract (crossed) on one side

The lesion is on the side with the proprioceptive loss

Cord compression (tumour, disc), myelitis (e.g. multiple sclerosis), cord trauma

Anterior spinal artery syndrome

Infarction affecting the anterior (ventral) thoracic spinal cord

Involvement of spinothalamic tracts bilaterally

Posterior columns spared

If the infarction extends down to the lumbar spinal cord, the lower limb reflexes are lost

Otherwise they become brisk because of the paraplegia caused by bilateral corticospinal tract involvement

Radicular distribution of cutaneous sensory loss

Radiculopathy

One of the clinical problems is that the distribution for nerve roots and individual peripheral nerves can be similar, e.g. C5 and axillary nerve, L4 and saphenous, L5 and common peroneal

Extensive sensory loss in one limb, not accounted for by a nerve root or a peripheral nerve

Consider a plexopathy (brachial or lumbar)

The motor features are likely to predominate

Sensory loss in the distribution of individual sensory or sensory and motor nerves

Mononeuropathy

Entrapment neuropathies of mixed nerves may present with sensory features only, or with motor and sensory features, which makes clinical diagnosis easier

For some nerves, you have to rely solely on clinical acumen – the nerve is not amenable to neurophysiological investigation, e.g. lateral cutaneous nerve of the thigh

Distal sensory loss in limbs

Polyneuropathy – classically ‘glove and stocking’ but may be much less marked (toes only) or much more marked, only sparing the back close to the spine

Multifocal polyneuropathies have features of a multiplicity of mononeuropathies

Familiarity with the areas of cutaneous sensation mediated by nerve roots (dermatomes – see Figs 14.15 and 14.16) is important for two reasons. First, it enables lesions of individual nerve roots to be diagnosed. Second, the level of a spinal cord lesion can be ascertained to some extent (see below).

Distal cutaneous sensory loss (touch; pinprick) in all four limbs, often in a ‘glove and stocking’ distribution, usually indicates a sensory polyneuropathy. Vibration sense and joint position sense may also be affected, and loss of reflexes, particularly the ankle reflexes, provides strong clinical support for a diagnosis of sensory polyneuropathy. Cervical spinal cord lesions sometimes produce quite widespread sensory symptoms in both hands which might make one think of peripheral nerve pathology, but the motor signs in the legs and possibly autonomic manifestations (sexual dysfunction, impaired bladder and bowel control) ought to clarify the situation. However, rarely, cervical spinal cord lesions can also give rise to distal lower limb sensory symptoms which can be misleading.

Spinal cord and cauda equina lesions

The characteristic sensory disturbance associated with compression of the cauda equina or spinal cord is one of loss of all modalities of sensation below the level of the compression. If the compression is of the cauda equina (e.g. a big central posterior intervertebral disc prolapse), all nerve roots below and possibly at the level of the lesion will be affected, including the buttocks and perineum. A severe spinal cord lesion (often compression, but any process which functionally transects the cord at one site) will result in a sensory level on the trunk (abdomen and back, or chest, including the arms if the lesion is between C5 and T1 spinal cord level) or on the neck. Knowledge of the anatomy of the dermatomes allows the spinal cord level (not the same as the spinal column level) to be determined. In spinal cord lesions of mild to moderate severity, the sensory level (which is less dense than in severe lesions) is some distance below the spinal cord level of the lesion. As the lesion evolves, the patient develops progressively worse sensory symptoms, first perceived at a level well below that of the lesion but which then extend up towards the level of the lesion. This process may not have been completed at the time the patient is evaluated and can sometimes lead to the wrong part of the spinal cord being imaged.

Brown-Séquard syndrome

This syndrome refers to the signs resulting from a focal lesion affecting the right or left half of the spinal cord, such as an intramedullary inflammatory or an extramedullary compressive lesion. Disruption of the descending corticospinal tract on the affected side results in an ipsilateral upper motor neurone disorder below the level of the lesion (commonly in one leg but a high cervical lesion would affect the arm as well). Involvement of the posterior columns on the affected side results in ipsilateral loss of vibration sense and joint position sense in the leg or arm and leg below the lesion. The spinothalamic tracts on the side of the lesion are affected, but sensory input into the spinothalamic tracts comes from pain and temperature afferents on the opposite side which cross over on entering the spinal cord, so loss of pinprick and temperature sensation occurs below the level of the lesion on the opposite side (Fig. 14.19). Some patients with mild lesions comment that while it is one leg which drags and feels weak and stiff, it is the other leg which has impaired sensation.

Figure 14.19 Brown-Séquard syndrome. Note the distribution of corticospinal, posterior column and lateral spinothalamic tract signs. The cord lesion is on the left side.

Central spinal cord lesion (especially syringomyelia)

A syrinx is a pathological tube-shaped cavity in the spinal cord, usually cervical and extending down into the thoracic area. It expands the spinal cord, but ascending and descending long tracts are unimpaired except in extreme cases. Anterior horn cells are damaged, leading to the motor manifestations of wasting and weakness of muscles in the arms and hands. Tendon reflex pathways are affected leading to upper limb reflex loss. There may be abnormalities of autonomic control of blood vessels and sweating in affected limbs. Most remarkable, however, are the patterns of sensory impairment. The classical findings are described by two adjectives: the sensory loss is dissociated; and a sensory level is found which is suspended. Dissociated sensory loss denotes loss of pain and temperature sensation with preservation of vibration and proprioception. The central cord lesion interrupts the sensory afferents which cross the middle of the spinal cord from dorsal roots on one side to spinothalamic tracts on the other side. Sensory afferents proceeding directly from dorsal roots into posterior columns are unaffected. Spinothalamic afferents which have already crossed below the lower limit of the lesion are also unaffected. This dictates that the loss of pinprick sensation will have an upper level corresponding approximately to the top of the syrinx, but there will also be a lower level, usually on the trunk, so the sensory loss is suspended by comparison with the situation in lesions affecting the spinothalamic tracts themselves (such as complete transverse cord lesions, the Brown-Séquard lesion or anterior spinal artery territory spinal cord infarction).

Anterior spinal artery territory spinal cord infarction

A major component of the arterial supply to much of the cord, particularly the thoracic spinal cord, comes from the anterior spinal artery, which receives its main blood supply via the artery of Adamkiewitz from the thoracic aorta. Spinal cord infarction is uncommon; when it occurs, it is usually the thoracic cord which is affected. Occlusion of the artery of Adamkiewitz may be atherosclerotic, arteritic or consequent upon dissection of the aorta. The result is infarction of the anterior (ventral) half of the spinal cord, over a variable length. The corticospinal tracts are involved bilaterally, resulting in abrupt-onset paraplegia. The major autonomic manifestations are loss of bladder and bowel control. The spinothalamic tracts are affected on both sides of the cord. Thus, there is dense loss of pinprick sensation with a sensory level on the trunk. The striking feature, in a numb paraplegic individual, is preservation of sensation mediated by the posterior columns – intact vibration and joint position sense in the toes and feet.

Patterns of sensory loss in lesions of the medulla

In the midbrain, pons and medulla, so many nuclei and nerve tracts are found in such restricted anatomical confines that inevitably the clinical manifestations resulting from small lesions in different parts vary substantially. Considering sensation in isolation, a lesion of the lateral medulla on one side may affect the spinothalamic tract on that side conveying pain sensation from the contralateral side of the body and, at the same time, affect the spinal tract and nucleus of the trigeminal nerve, which mediates pain on the ipsilateral side of the face.

Hemianaesthesia

A lesion affecting the sensory afferent pathways rostral to the principal sensory nucleus of the trigeminal nerve in the pons (i.e. in the midbrain, diencephalon, thalamus or internal capsule) will result in a hemianaesthesia: loss of sensation on the whole of one side of the body including the head and face. A large lesion, such as a middle cerebral artery territory ischaemic stroke affecting the whole of the primary sensory cortex, will have the same effect. Smaller lesions in sensory cortex will affect sensation (all modalities) in only part of one side of the body.

Cognitive function

There is a risk in neurological examination that cognition may be neglected. It is a useful simplification to divide domains of cognition into those which are distributed and those which are localized. The anatomical substrates of distributed cognitive functions are bilateral and widespread in the brain. An implication is that a single focal neurological lesion will have little perceptible impact on that function. In contrast, a focal lesion in a particular place will have a major effect on a localized cognitive function.

The two major syndromes of cognitive impairment, which may be accompanied by no neurological signs, are dementia and delirium. They are covered in Chapter 6. In this section, emphasis is placed on cognitive deficits which, to some extent, have localizing value and which may be seen in patients with focal cerebral lesions as well as those with more generalized neurodegenerative disorders.

Amnesia

Memory is a distributed cognitive function. Dense amnesia requires bilateral hemisphere lesions, but those lesions may be very focal – bilateral thalamic infarction, or damage to the mamillothalamic tracts in Wernicke’s encephalopathy, can cause devastating amnesia – and the anatomy of memory in each hemisphere is localized and well defined. Furthermore, unilateral lesions, such as a posterior cerebral artery occlusion causing temporal lobe infarction, do have discernible effects on memory. Normal episodic memory (memory of events which have been personally experienced) depends on integrity of the hippocampi and entorhinal cortex in the temporal lobes, the fornices, the thalami and the mamillary bodies. Anterior temporal lobes subserve semantic memory (memory for facts, learning and general knowledge). Verbal memory is dependent on the left temporal lobe, visual memory on the right temporal lobe. Some important causes of amnesia are listed in Table 14.14. Amnesia emerges mainly from the history taken from an informant rather than from the patient. Episodic memory may be assessed by testing recall of a name and address that the patient has registered; and by testing the patient’s recall of events from his past, both recent and distant.

Table 14.14 Some causes of amnesia

Cause	Comment
Acute
Transient global amnesia	The name describes well what happens; the pathology remains obscure; imaging indicates a hippocampal process
Transient epileptic amnesia	Here amnesia is the seizure
Epilepsy more generally	Temporal lobe seizures may involve amnesia; postictal amnesia follows any generalized convulsion
Closed head injury	Concussion involves retrograde and anterograde post-traumatic amnesia
Drugs: benzodiazepines, alcohol	Amnesia can occur without significant impairment of alertness
Chronic
Hippocampal damage
Herpes simplex encephalitis	Bilateral temporal lobe damage
Limbic encephalitis	Bilateral temporal lobe damage
Cerebral anoxia
Temporal lobectomy with a lesion in the other temporal lobe	Should not happen nowadays in modern practice because of improvements in preoperative assessment
Bilateral posterior cerebral artery territory infarction
Closed head injury	Bilateral temporal lobe damage is common
Early Alzheimer’s disease	Later there are other prominent cognitive deficits as well
Diencephalic damage
Korsakoff’s syndrome	This is what results from untreated Wernicke’s encephalopathy, due to thiamine deficiency
Third ventricular tumours and cysts	Potentially affecting the fornices and thalami bilaterally
Bilateral thalamic infarction	Either two separate events or, if the bilateral paramedian thalamosubthalamic arteries of Percheron branch from one common vessel (a not uncommon variant), one stroke
Subarachnoid haemorrhage from anterior communicating artery aneurysm