and family history of migraine was used to make a diagnosis of migraine. This patient’s symptoms were of instantaneous onset and were related to a ruptured berry aneurysm causing subarachnoid haemorrhage (bleeding into the subarachnoid space – the space beneath the outer lining of the brain, referred to as the dura mater, and the surface of the brain).

A past history of a medical problem does not preclude the patient suffering from

• A past history of an illness or risk factors for an illness only increase the likelihood that the patient has a particular problem; they should not be used to make a diagnosis.

• The nature and distribution of the symptoms can only localise the problem within the nervous system and cannot infer a particular pathological diagnosis.

a totally unrelated illness. The approach of using the past history to influence the diagnosis of the current problem often leads to a delay in diagnosing new problems in patients with chronic diseases. In most instances ‘prior probability’ is correct, and this can lull clinicians into thinking that they are clever when in fact it was difficult for them to be wrong even if they did not obtain a detailed history. Typical examples of this are an older person with a hemiparesis with the most likely cause being a stroke and the general practitioner (GP) who diagnoses most patients as having a tension-type headache and is correct the vast majority of the time simply because most patients attending a GP with headache do in fact suffer from tension-type headache.

The age of the patient and the past, family and social history simply increase the likelihood of a particular illness being present. This information should be regarded as ‘circumstantial evidence’. As in law, where many innocent people have been found guilty on the basis of circumstantial evidence, in medicine many incorrect diagnoses have been made using the age of the patient and the past, family, social and medication history to make a diagnosis.

Spencer [1] stated that it is not possible to learn how to take an effective history from a textbook. The clinical environment is the only setting in which the skills of history taking, physical examination, clinical reasoning, decision making, empathy and professionalism can be taught and learnt as an integrated whole. Although this is correct, one could use the analogy of learning to play golf: you can either hack away for years to teach yourself or you can have lessons that will make the practice more effective.

Traditionally, students have been taught to ask a long list of neurological questions about headache, dizziness, weakness, numbness etc in the forlorn hope that, after this ‘fishing expedition’ (also referred to as ‘looking for the pony’¹) [2], a diagnosis will be apparent. In other words, in the hope of finding the diagnosis (‘the pony’), one collects a large list of answers to numerous specific questions that largely relate to the nature of the symptoms with little understanding about what the answers represent. It has been suggested that students should be taught to take a history this way and then taught not to take it that way. I disagree. I would like to recommentd that students should be taught how to take a history in a way that is meaningful to them rather than just collecting useless information they do not know how to use.

PRINCIPLES OF NEUROLOGICAL HISTORY TAKING

When obtaining the history from a patient with a neurological problem it is important to establish whether the problem is:

• a monophasic illness

• intermittent symptoms or recurrent episodes.

An alternative method of obtaining the history in patients presenting with intermittent disturbances of neurological function or recurrent episodes, e.g. epilepsy or headache, is recommended. In essence, with intermittent disturbances it is better to obtain a blow-by-blow description of several individual episodes. This alternative approach is described in Chapter 7, ‘Episodic disturbances of neurological function’ and Chapter 8, ‘Seizures and epilepsy’.

Having established that the problem is a monophasic illness, the three basic principles of history taking are simple:

1. Define the likely underlying pathological basis by eliciting the mode of onset, progression and duration of each and every symptom (i.e. the time course of the illness).

2. Establish the site of the disorder within the nervous system by determining the nature and distribution of symptoms.

3. Elicit other facts that may either establish a cause for the problem or, more importantly, influence subsequent management of the patient. This includes the family history, past history, coexistent medical problems, prescribed drugs and natural remedies the patient is taking, social factors and the patient’s concerns.

Difficulties making a diagnosis are almost always the result of failure to establish the mode of onset, progression and duration of symptoms.

Some patients are not capable of giving an accurate history. This is often (but not always) due to the presence of an inability to speak the language, dementia, confusion or amnesia. In these circumstances it is necessary to question a relative or an eyewitness. If that is not possible, one has no choice but to use circumstantial evidence (the past and family history) and prior probability (certain conditions affect particular people of a certain sex and age) to come to a likely diagnosis.

THE UNDERLYING PATHOLOGICAL PROCESS: MODE OF ONSET, DURATION AND PROGRESSION OF SYMPTOMS

Different pathological processes evolve over variable periods of time and it is this variability that can be used to determine the most likely pathology. Three modes of onset can be loosely defined: sudden onset within seconds to minutes, gradual onset over hours to days and a very gradual onset over months to years (see Figure 2.1). The expression ‘mode of onset’ refers to the time for all symptoms to FULLY develop in terms of either their intensity and/or their distribution.

FIGURE 2.1 The three ‘modes of onset’ of an illness: A acute, seconds to minutes; B subacute, hours to days; C chronic, months to years

The pathological processes that reflect these modes of onset are:

A Instantaneous – seconds, rarely minutes

• Electrical: an epileptic seizure or an arrhythmia such as a tachyarrhythmia (fast heart beat), bradyarrhythmia (slow heart beat) or complete heart block (no impulse between the right atrium and ventricles, the Stokes–Adams attack)

• Vascular: subarachnoid haemorrhage, cerebral embolus

• Mechanical: trauma, a slipped intervertebral disc or positional vertigo

B Subacute – hours to days

• Infective: meningitis, encephalitis

• Inflammatory: multiple sclerosis, acute inflammatory neuropathies

• Metabolic disorders: hyponatraemia, diabetic coma

C Chronic – months to years

• Neoplastic: benign and occasionally malignant tumours

• Degenerative: cervical spondylitic myelopathy and the various genetic disorders

• Chronic endocrine problems: hypothyroidism, Cushing’s disease, pituitary disorders

• Chronic inflammatory/infective processes: polymyositis, chronic inflammatory demyelinating peripheral neuropathies, cryptococcal or tuberculous meningitis

The majority of diseases that clinicians encounter fit into one of these three basic patterns, but it is important to remember that they are only a guide and there are always exceptions to the rule.

Exceptions to the rule include:

• Symptoms such as diplopia (double vision) and vertigo will, as a result of their very nature, always begin abruptly and need not necessarily indicate a pathological process with a vascular or mechanical basis (see the section ‘The nature and distribution of symptoms’).

• At time, neoplastic disorders can present with a very rapid evolution of symptoms as a result of a seizure and the rapid onset of a focal neurological deficit after the seizure; tumours can also appear to evolve more rapidly when there is a superimposed mechanical shift due to the mass effect.

• Vascular disorders can have a slower onset: for example, the stroke-in-evolution that may or may not be stepwise; the intracerebral haemorrhage that evolves over many minutes; the subdural that develops over hours to days (although here the bleeding results in a mass lesion); or the giant aneurysm that behaves as a tumour with symptoms due to the mass.

• In older patients with a chronic disease the deterioration is so slow that it is assumed that their increasing disability is simply related to old age until there is a sudden crisis, such as a fall where they are unable to get up. Patients present under these circumstances with an apparent illness of sudden onset, where in reality it is simply the ‘straw that broke the camel’s back’ phenomenon. The true nature is only clarified when a careful and detailed history of slowly evolving disability is obtained.

There are two circumstances where it is not possible to establish the exact time of onset of the initial symptom(s):

• Firstly, if the symptoms are present on awakening, even if the patient awoke at an unusual hour, unless you can determine that the symptoms awoke the patient (and this is very unlikely). The best estimate for the onset is the time between falling asleep and awakening.

• Secondly, if the symptoms are only noticeable when there is an external stimulus (e.g., the patient becomes aware of numbness only when they touch their face).

In this situation it is imperative to elicit whether the symptoms have progressed since first noticed. Progression can either be more intense symptoms or spread of the symptoms to other parts of the body.

THE NATURE AND DISTRIBUTION OF SYMPTOMS

Neurologists use the nature of the symptoms and their distribution over the body to determine which part of the nervous system is involved in the disease process. In doing this it is important to remember that many patients use terms differently from the medical profession and, therefore, it is important to clarify what the patient means.

• Variability of weakness with exercise suggests the neuromuscular junction and myasthenia gravis or Lambert–Eaton syndrome.⁴ Increased weakness with exercise indicates possible myasthenia gravis, while increased strength (and increased reflexes if examined before and after exercise) with exercise the Lambert–Eaton syndrome.

• A loss of speech is referred to as aphasia, while impairment of speech is referred to as dysphasia affecting the production and/or comprehension of written or spoken language. This almost invariably indicates a dominant hemisphere problem, usually cortical. Very rarely, a subcortical or even a thalamic problem can cause dysphasia.

SYMPTOMS THAT ONLY POINT TO INVOLVEMENT OF A PARTICULAR PATHWAY

• Vertigo (room or head spinning): vestibular system, anywhere from the inner ear through the vestibular nerve to the brainstem and the central vestibular cortex in the temporal lobe

• Weakness: motor pathway between the cerebral cortex and the muscle

• Altered sensation: sensory pathways between the peripheral nerves and the cerebral cortex

Note: Spontaneous symptoms such as tingling or paraesthesia imply a sensory problem but do not differentiate between the pathways of pain and temperature and those of vibration and proprioception. Symptoms, such as a limb that feels but does not look swollen, skin that is stretched tight or that feels as if there is a tight stocking or glove around the limb, and instability in the dark or when the eyes are closed, are characteristic of the problems affecting the proprioceptive pathways. An inability to feel the temperature or to experience pain clearly points to involvement of the spinothalamic pathways.

• Marked wasting or fasciculations (visible twitching) of muscles: the lower motor neuron from the anterior horn cells in the spinal cord through the anterior nerve roots, brachial or lumbrosacral plexus and peripheral nerves

NON-SPECIFIC SYMPTOMS

• Dysarthria: has no localising value (other than it clearly indicates the problem is above the level of the foramen magnum). It can result from non-dominant hemisphere lesions, deep dominant hemisphere lesions, brainstem pathology and problems affecting the 9th, 10th and 12th nerves, the neuromuscular junction and even disorders of muscle. Neurologists can often differentiate between the different causes of dysarthria but this is difficult for non-neurologists.

• Anosmia: is the loss of the sense of smell; if it is of neurological origin it points to involvement of the olfactory pathway, but in most patients it does not relate to any disorder of the nervous system but is rather due to local nasal pathology.

• Exacerbation of symptoms from heat and exercise: transient worsening of symptoms with heat or exercise that is not relieved by immediate rest is very common with many neurological disorders. One of the most common conditions in which this is a feature is multiple sclerosis.

• Ataxia (or unsteadiness on the legs): is a very non-specific symptom. Although it suggests a cerebellar problem, it can also be present in patients with arthritis in the joints of the legs, weakness or a proprioceptive disturbance in the legs and in patients with vertigo that is vestibular and not cerebellar in origin. A useful question to ask is whether the instability relates to a feeling of instability in the head, indicating probable involvement of the vestibular system, hypotension or a cerebellar problem, or to a sense of unsteadiness in the legs in the absence of any altered sensation in the head, suggesting a problem of weakness or sensory disturbance in the legs.

• Pain: is most often related to non-neurological disorders. If it is of neurological origin, it is almost invariably an indication of involvement of the peripheral nervous system as central pain syndromes are exceedingly rare. Central pain syndromes develop after thalamic infarction in which there is pain in the distribution of the contralateral hemi-sensory loss.

• Urinary or bowel sphincter disturbance: sphincter disturbance is a prominent symptom of intrinsic spinal cord problems (as opposed to extrinsic cord compression in which sphincter disturbance develops late), sacral nerve root lesions or autonomic nervous system involvement. However, in females urinary incontinence is more often of gynaecological origin and not related to a neurological problem.

• Dysphagia: (or difficulty swallowing) can occur with brainstem (medulla) or hemisphere problems and is therefore in itself a poor localising symptom.

Weakness with sensory symptoms immediately indicates that the problem CANNOT be related to diseases of muscle, the neuromuscular junction or anterior horn cell within the spinal cord, as these sites result in pure motor syndromes.

The distribution of symptoms

As already discussed in Chapter 1, ‘Clinically oriented neuroanatomy’, ALWAYS think about the underlying neuroanatomy that the nature and distribution of symptoms represents. In most instances the history can assist in establishing whether the pathology is affecting the brain or spinal cord (in the central nervous system) or peripheral nervous system.

As you take the history, think of the nervous system as a map grid with the meridians of longitude and parallels of latitude that were discussed in Chapter 1, ‘Clinically oriented neuroanatomy’. Although the neurological examination is far more important when it comes to accurate localisation, many patients present with transient neurological symptoms and there may not be any neurological signs. For example, establishing from the history that a patient has weakness affecting the entire left side of the body including the face clearly indicates that the problem must be in the central nervous system and on the contralateral side above the mid pons.

By defining the meridians of longitude and the parallels of latitude that the symptoms (and subsequently the signs, if present) represent, it is possible to localise the site of the problem in the nervous system in most patients.

PATTERNS OF WEAKNESS

If the symptom is weakness, ask questions to define the exact pattern of weakness. If it is confined to one limb, ascertain if it is the whole limb or only part of the limb that is affected. If the whole limb is weak, this is more suggestive of a central nervous system problem. If only part of the limb is weak, then it is more likely (but not always) related to involvement of the peripheral nervous system (nerve root, an individual nerve, the brachial plexus in the arm or lumbosacral plexus in the leg). Establish what part of the limb is weak. Muscle wasting and/or fasciculations (involuntary twitching of parts of muscles) are both occasionally observed by patients and localise the problem to the lower motor or peripheral nervous system.

An example of how the pattern of weakness can help to localise the problem while taking a history is shown in Case 2.3.

The patterns of weakness that indicate involvement of a particular part of the nervous system include:

• Weakness confined to one limb: weakness affecting the entire arm or the entire leg, particularly when it begins suddenly, is most likely to be due to a central rather than a peripheral nervous system problem. The history is not particularly useful when there is a focal weakness in a limb. Focal weakness in a limb can be either of central or peripheral nervous system origin and a neurological examination is needed to sort out the various causes. On the other hand, establishing exactly what part of the limb is weak can narrow down the possibilities if the problem is in the PNS.

• Weakness of the hand or forearm: C7, C8, T1 nerve root, median, ulnar or radial nerve (Case 2.4 illustrates weakness in the right arm accompanied by some sensory loss.)

• Weakness of the upper arm or shoulder: C5–C6 nerve root, axillary, musculocutaneous or suprascapular nerve problems

• Weakness of the upper leg: L2, L3, L4 nerve root or femoral nerve

• Weakness the lower part of the leg: L5–S1 nerve root, sciatic, common peroneal or posterior tibial nerve problem.

CASE 2.3 A 55-year-old man presents with ‘right-sided weakness’

If the weakness involves the whole leg, then it most likely reflects an upper motor neuron or central nervous system problem, above the level of L2 in the lumbar spinal cord. If the ipsilateral arm is affected, this places the pathology above the level of C5 in the cervical spinal cord and, if the ipsilateral face is also affected, the lesion is above the facial nerve nucleus in the contralateral mid pons of the brainstem. In the absence of any additional symptoms, this is as far up as we can localise the problem. On the other hand, if the patient has impaired speech in the form of dysphasia, this indicates involvement of the speech cortex. The right-sided weakness is the meridian of longitude indicating involvement of the motor pathway. The dysphasia is the parallel of latitude indicating involvement of the cortical structures that form the basis of speech.

• Hemiparesis: the abrupt onset of weakness of the arm and leg with or without facial involvement is almost certainly a central nervous (upper motor neuron) system problem. Most often it is related to a problem in the contralateral hemisphere, less likely the contralateral brainstem and very rarely in the ipsilateral spinal cord above the level of C5. Slowly evolving hemiparesis could be of central or peripheral nervous system origin.

• Paraparesis: weakness confined to both legs is most often related to a spinal cord problem or a lower motor neuron problem such as a peripheral neuropathy.

• Quadriparesis: four-limb weakness indicates a cervical spinal cord problem above the C5 level, less often a peripheral neuropathy or muscle disease.

Obviously, once a patient has symptoms affecting the cranial nerves, vision, speech, hearing, vertigo, memory or cognition, the problem CANNOT be confined to the spinal cord.

PATTERNS OF SENSORY SYMPTOMS

When a patient complains of numbness in a hand, all we can ascertain from this is that the problem must be somewhere between the peripheral nerve and the contralateral cerebral cortex. On the other hand, if we then ask the patient to clarify the exact area of numbness we can ascertain whether the numbness is in the distribution of a single nerve or nerve root or whether in fact it involves one of the sensory pathways, differentiating between sensory symptoms arising in the peripheral versus the central nervous system, respectively.

For example, a patient complains of numbness in the hand. If the numbness affects the medial 1½ fingers on both the palmar and dorsal aspects of the fingers and the medial aspect of the hand up to the wrist, this pattern of sensory loss is typical of an ulnar lesion (see Figures 1.14 and 1.15). A second example is the patient who

CASE 2.4 A young man with weakness in the right arm and focal sensory loss

A 20-year-old man has fallen asleep in a chair after a heavy night of drinking. He awakens the next morning and notices severe weakness in his right arm. He is unable to extend his wrist and fingers and his hand grip is very weak. He is not aware of any pain but there is a small area of sensory loss between his thumb and index finger. He is right-handed and his speech is normal.

• The patient has noticed his symptoms on waking and therefore the exact mode of onset cannot be determined except to say that they arose sometime between when he fell asleep and when he woke. The onset therefore could have been very sudden or it could have come on gradually over minutes or hours.

• The patient has a focal weakness in the right arm with an inability to extend the wrist and fingers. This occurs with a stroke, a radial nerve palsy or with a C7 radiculopathy. The weakness is usually mild with a C7 radiculopathy and usually there is associated pain. Severe weakness in the right hand in a right-handed person due to a central nervous system problem will almost invariably be associated with a severe speech disturbance and a wrist drop is unusual for a stroke. However it is the very focal sensory loss between the first and second fingers that enables the correct diagnosis of a radial nerve palsy. As shown in Figure 1.15, the area of skin between the first and second digits is supplied by the superficial radial nerve. C7 radiculopathy would produce sensory loss affecting the middle three digits of the hand.

CASE 2.5 A woman with numbness and tinging

A 25-year-old woman presents with a gradual onset of numbness and tingling commencing in the toes and spreading over 3 days to affect her body from the breasts down. She has also noticed difficulty urinating and has been constipated.

• The distribution of the sensory symptoms clearly indicates involvement of the sensory pathways because they affect both the legs and the trunk and cannot represent problems associated with individual nerves or nerve roots.

• Sensory symptoms do not occur on the entire trunk in problems affecting the peripheral nervous system, but sensory disturbance on either side of the midline can be seen in, for example, diabetic truncal neuropathy. This gives a band of sensory loss extending a few centimetres on either side of the midline rather than sensory loss affecting the whole of the trunk.

• The sensory symptoms extend up to the level of the breasts, which is consistent with a lesion at the level of T4 in the thoracic spinal cord. The disturbance of sphincter function also indicates that the problem is in the spinal cord. The mode of onset is gradual over several days and this suggests an inflammatory or infective process.

complains of numbness in the leg, which in itself cannot help localise the problem, whereas numbness confined to the lateral aspect of the thigh below the groin and above the knee is the area supplied by the lateral cutaneous nerve of the thigh (see Figure 1.20). Case 2.5 illustrates numbness originating from a central nervous system problem.

Sensory symptoms affecting the ipsilateral leg, arm and the face indicate a lesion above the contralateral 5th nerve nucleus in the brainstem.

Patients are often referred with suspected tarsal tunnel syndrome due to compression of the medial or lateral plantar nerves at the level of the medial malleolus when they have symptoms affecting the top as well as the sole of the foot, clearly indicating that the problem is beyond the distribution of the medial or lateral plantar nerves, which only supply the sole of the foot, and therefore the problem cannot be tarsal tunnel syndrome.