The area just in front of the central sulcus, referred to as the pre-central gyrus (see Figure 5.1), is the origin of the motor fibres that innervate the muscles on the opposite side of the body. This pathway is referred to as the corticospinal tract and it crosses the midline at the level of the foramen magnum, the junction of the lower end of the brainstem and the upper end of the cervical spinal cord. Lesions affecting the pre-central gyrus will result in a contralateral hemiparesis affecting the face, arm and leg although, one limb may be weaker than the other and the face may be affected to a variable degree (partial weakness) or with hemiplegia (total weakness).

The clues that the hemiparesis is derived from a lesion in the frontal lobe are:

• conjugate eye deviation, in which the eyes look away from the side of the weakness and towards the side of the lesion due to involvement of the area of the frontal lobe that controls conjugate deviation of the eyes to the opposite side

• cortical sensory signs due to associated involvement of the parietal lobe on that side

• non-fluent dysphasia with dominant hemisphere lesions.

Very rarely, an irritative lesion can result in a contralateral hemiparesis with the eyes deviated to the side of the weakness and away from the side of the pathology, mimicking a pontine lesion in the brainstem where there is an area responsible for conjugate deviation of the eyes to the same side. When this area of the brainstem is affected the eyes deviate away from the side of the lesion and towards the side of the paralysis.

Changes to personality or behaviour

The pre-frontal region is that part of the frontal lobes anterior to the motor cortex and the motor speech area. Diseases affecting this region of the frontal lobe result in changes to personality or behaviour best summarised by the phrase ‘he/she is not him/herself’.

These patients can lose spontaneity and initiative and appear apathetic and depressed or, at the other end of the spectrum, patients can appear to ‘have a short fuse’. In this situation patients can become aggressive and violent, even after a trivial incident. This is seen following some head injuries. Patients with frontal lobe pathology can develop an elevated mood and behave inappropriately, such as the vicar’s wife who begins to tell dirty jokes and who was subsequently diagnosed with a meningioma (a benign tumour) in the frontal lobe.

If the olfactory tracts that lie beneath the frontal lobe are also affected, there can be an associated unilateral or bilateral anosmia (loss of the sense of smell).

An inability to perform acts voluntarily or to make decisions is seen in patients with pre-frontal problems and is termed abulia, reflecting pathology in the medial aspect of the frontal lobes. Abulia sometimes occurs with a subarachnoid haemorrhage (bleeding into the subarachnoid space) from vasospasm of the anterior cerebral artery related to a ruptured berry aneurysm on the anterior communicating artery (see Chapter 10, ‘Cerebrovascular disease’).

Difficulty walking

Another presentation of patients with frontal lobe pathology is apraxia of gait. The history is one of progressive difficulty walking in the absence of any weakness, sensory disturbance, ataxia or extrapyramidal dysfunction to account for the difficulty walking. It is as if the patient has forgotten how to walk. This is discussed in Chapter 12, ‘Back pain and common leg problems with or without difficulty walking’.

There are a number of frontal lobe signs, referred to as primitive reflexes, because they are present in normal babies and may or may not be seen in patients with frontal lobe pathology. These include:

• a grasp reflex, where the patient involuntarily grasps an object (usually the examiner’s hand) placed in the palm of their hand

• a positive palmo-mental reflex, where the palm of the hand is stroked and there is retraction of the ipsilateral chin beneath the lips

• a pout reflex, where the patient purses the lips when a stimulus is applied to them.

Although changes in personality and behaviour may be one of the presenting symptoms of dementia, severe depression can produce a similar clinical picture termed ‘pseudo-dementia’.

THE PARIETAL LOBES

Patients with parietal lobe problems may present in a number of ways:

• speech disturbance such as fluent dysphasia and, if Wernicke’s area in the posterior temporal lobe is also affected, the patient may also present with confusion (discussed in the section ‘Disturbances of speech’ below)

• disturbances of vision in the contralateral visual field

• lost and disoriented patients who appear to be lost or disorientated even in a familiar environment

• a concerned relative brings the patient for assessment, as some patients are not even aware of any problem at all and the problem is only detected when another person observes that there is something wrong.

Visual disturbances can occur in both dominant and non-dominant hemisphere problems; dysphasia is a feature of dominant hemisphere problems; being lost, disoriented and unaware that anything is amiss are very typical features of problems in the non-dominant hemisphere.

In both the dominant and non-dominant hemispheres, there are visual pathways that pass through and sensory pathways that terminate in the parietal lobe. If the so-called ‘primary pathway’ is affected, there will be a contralateral loss of function. If the ‘primary pathway’ is intact but the so-called ‘secondary association areas’ are affected, there will be a contralateral inattention with double simultaneous stimuli where the patient is not aware of the stimulus on one side when the other side is stimulated in the same manner simultaneously.

Speech disturbance (dysphasia) and the term RAAF (an abbreviation for the Royal Australian Air Force) best describe the features of problems in the dominant hemisphere, while the term ‘lost in space’ is the easy way to remember the characteristics of non-dominant parietal lobe problems (see Table 5.1). RAAF refers to the clinical findings seen in dominant parietal lobe problems and, in its pure form, is referred to as Gerstmann’s syndrome (for an explanation of RAAF, see ‘Gerstmann’s syndrome’ below).

TABLE 5.1

Summary of the clinical features with lesions of the dominant and non-dominant parietal lobes

^∗It can be seen that sensory and visual symptoms together with the unique parietal cortical signs are common to both the dominant and non-dominant parietal lobes. It is the speech disturbance and the parietal lobe abnormalities associated with Gerstmann’s syndrome in the dominant hemisphere and the characteristic abnormalities seen in the non-dominant hemisphere (referred to as ‘lost in space’) that differentiate between the two hemispheres.

^∗∗Either loss of vision in the opposite visual field (hemianopia) or loss of vision in the upper or lower aspect of the visual field on the opposite side (quadrantanopia).

Abnormalities of vision

• Contralateral loss of vision. The optic radiation from the contralateral visual field passes through the parietal lobes to the occipital lobe (see Figure 5.1). If the ‘primary pathways’ are affected, there will be a loss of vision on the contralateral side resulting in a lower quadrantanopia if only the parietal lobe is affected, but often the optic radiation fibres in the temporal lobe are also affected and the resulting deficit is a contralateral homonymous (the visual field disturbance is identical when each eye is tested separately) hemianopia.

• Contralateral visual inattention. If the ‘primary visual pathways’ are preserved, but the so-called ‘secondary association areas’ are affected, there will be visual inattention elicited with double simultaneous stimuli. The patient is unable to appreciate the visual stimulus in one visual field, usually a moving finger applied simultaneously to both visual fields, but can if only one visual field is stimulated at a time.

Abnormalities of sensation

Although abnormalities of sensation are commonly detected on examination of patients with parietal lobe problems, they are only occasionally the presenting symptom.

• Contralateral loss of sensation affecting the primary sensory modalities of vibration and proprioception, pain and temperature

• Contralateral sensory inattention where the patient cannot appreciate sensation on one side of the body when the stimulus is applied simultaneously to both sides

• Unique parietal sensory phenomena

• Impairment of 2-point discrimination

• Impaired stereognosis

• Impaired graphaesthesia

The sensory pathways from the body terminate in the contralateral post-central gyrus of the parietal lobes. If the so-called ‘primary sensory pathways’ in the parietal lobes are affected there will be abnormal sensation on the opposite side of the body, resulting in loss or impairment of vibration and proprioception with either cortical or deep hemisphere parietal lobe problems and/or loss or impairment of pain and temperature sensation with deep hemisphere but not cortical parietal lobe problems.

If the ‘primary pathways’ are not affected, but the area of the parietal lobe that interprets these sensory stimuli (referred to in this chapter as the ‘secondary association areas’) is involved in the pathological process, the resulting abnormality will be a loss of appreciation of sensation elicited with double simultaneous stimulation termed sensory inattention. Here, the examiner applies the same stimulus to both sides of the body simultaneously. This is usually performed by stroking the skin with a finger. Patients with sensory inattention do not notice the sensory stimulus on the contralateral side of the body to the pathology when both sides are stimulated simultaneously but can appreciate the sensory stimulus when only one side is stimulated.

Although abnormalities of vibration and proprioception can occur in cortical lesions, the detection of impaired vibration and proprioception cannot localise the problem to the cortex. If the primary sensory modalities of pain, temperature, vibration and proprioception are normal or only mildly affected, it is possible to perform more detailed sensory testing looking for abnormalities seen with contralateral parietal cortical lesions. The three cortical signs consist of:

1. Impairment of stereognosis: the patient is unable to appreciate the shape and size of an object, for example a pen or a coin, placed in the affected hand. Proprioception must not be affected, otherwise the inability to identify the object would reflect impairment of the proprioceptive pathway and not necessarily the contralateral parietal cortex as the site of abnormality.

2. Impairment of graphaesthesia: the patient is unable to identify a number drawn on the palm of the contralateral affected hand. The drawing must be greater than 4 cm in size and initially a number is drawn on the palm of the hand while the patient watches. The patient is then instructed to close their eyes and identify another number drawn on the palm. It is easier for patients to identify numbers if their palm is facing towards them and not the examiner. If light touch is severely impaired, abnormal graphaesthesia may occur and not indicate a cortical problem.

3. Impairment of 2-point discrimination: an inability to distinguish two points from one. This can be tested on any part of the body but the distance between the two points varies greatly from 1 mm on the tip of the tongue to 20–30 mm on the dorsum of the hands and feet [1]. The most useful site to test 2-point discrimination is on the fingertips where the normal distance is 3–5 mm. It is recommended to test the opposite hand (if it is normal) to determine the distance between the two points in this particular patient as this can vary from patient to patient depending on the age of the patient.

The above sensory and visual abnormalities occur with pathology in either the dominant (usually left) or non-dominant hemisphere with the three cortical signs contralateral to the side of the pathology.

The dominant hemisphere

In addition to the sensory and/or visual abnormalities with or without the three cortical sensory signs described above, patients with dominant hemisphere lesions may have a speech disturbance termed dysphasia and some or all of the signs of what has been referred to as Gerstmann’s syndrome.

DISTURBANCES OF SPEECH

Clinicians use abnormalities of speech to localise the problem within the nervous system. On the other hand, speech therapists assess abnormalities of speech in a completely different manner and more from the therapeutic point of view. A simplified approach is shown in Figure 5.2.

FIGURE 5.2 Simplified approach to speech disturbances The first step is to establish whether the patient is suffering from dysarthria, which has poor localising value, or dysphasia, which localises to the dominant hemisphere:

• Dysarthria refers to difficulty in speaking because of impairment of the organs of speech or their innervation [4]. Dysarthria occurs with problems in many areas of the brain, including the frontal lobes or parietal lobes, cortex or deep within the subcortical white matter of either the dominant or non-dominant hemisphere. Dysarthria also occurs with brainstem and cerebellar problems, disorders of the 9th, 10th and 12th cranial nerves, disorders of the neuromuscular junction or even diseases affecting the face, tongue or palatal muscles. Although experienced neurologists may be able to differentiate between the various types of dysarthria, this is difficult for non-neurologists.

• Dysphasia is an impairment of the ability to understand and use the symbols of language, both spoken and written [4]. If the speech disturbance results in a total loss of speech, it is referred to as aphasia. Dysphasia occurs with dominant hemisphere problems (see Figure 5.3): in 90% of right-handed people and 50% of left-handed people this is the left hemisphere.

FIGURE 5.3 Lateral view of the dominant hemisphere showing the three main areas where pathological processes can produce the more commonly encountered types of dysphasia
A Temporal lobe: fluent, sensory, receptive, Wernicke’s; B Parietal lobe: fluent, amnestic, nominal; C Frontal lobe: non-fluent, motor, expressive, Broca’s Note: In this illustration the sites for speech are not strictly anatomically correct, but are simply located within the relevant lobe. Various terms have been applied to the different abnormalities of speech referred to as dysphasia.

The simplest classification to understand is the one that reflects the abnormality of speech encountered: non-fluent (C) or fluent with (A) or without (B) comprehension difficulties.

A If the pathology is in the posterior aspect of the dominant temporal lobe (area A, Figure 5.3), the patient has word deafness where they cannot monitor their own speech or understand what is said to them and the patient will appear to be totally confused. Speech is fluent with literal (letters) and verbal (words) paraphasic errors where letters of some words or entire words are replaced by other letters or words. Non-existent words, referred to as neologisms, are invented. As patients are unable to monitor their own speech the words are often said out of sequence, described as a word salad. An example of a literal paraphasic error is where the patient says ‘mouse’ instead of ‘house’, and an example of a verbal paraphasic error is where the patient says ‘the sky is brown’. An example of a neologism is ‘rumpstle’.

B If the temporal lobe is not affected and the pathology lies within the parietal lobe (area B, Figure 5.3), the resulting speech disturbance will be less marked. As the problem is behind the central sulcus the speech will be fluent, but the patient can understand what is being said to them and they can monitor their own speech. There are occasional literal and verbal paraphasic errors, but neologisms and word salad are not a feature. These patients have a curious deficit, where they are unable to name objects, thus the term nominal dysphasia. This type of dysphasia may be a disconnection syndrome [1]. When patients are asked to name a pen or a part of a wristwatch, for example, they struggle to find the appropriate word, but they can often but not always exhibit an understanding of how the object is used.

C As the motor cortex is very closely related to the area in the frontal lobe that is involved with the production of speech (area C, Figure 5.3), a frontal lobe disorder of speech is almost invariably associated with a contralateral hemiparesis (partial weakness) or hemiplegia (total weakness). The patient can understand what is being said; they know exactly what they want to say but are unable to produce the words. However, they are not mute, which is the inability to produce sound. They give the appearance of having a stutter of variable severity reflecting the severity of the underlying speech disturbance. The patient frequently becomes very frustrated at the inability to express themselves. If the examiner shows the patient a pencil, for example, and asks them to name the object, the patient can be seen to be struggling to express the correct word. If after several attempts the examiner correctly names the object, the patient will nod in agreement.

Patients who are unable to speak are also unable to produce written language, even in the absence of paralysis of the arm.

The resulting speech disturbance that occurs if all three areas are affected is referred to as total or global dysphasia. In this situation, the patient may be able to understand or utter a few words but is unable to follow simple commands and unable to read or write.

There are a number of speech disturbances that are referred to as disconnection syndromes. These include conduction aphasia, pure word deafness and pure word blindness, to name just a few. These are believed to result from lesions affecting the association pathways joining the primary receptive areas to the language areas and not from lesions affecting the cortical language areas. A detailed discussion of these seldom encountered speech abnormalities is beyond the scope of this book, but can be found in textbooks [1–3].

GERSTMANN’S SYNDROME

Gerstmann’s syndrome refers to a constellation of abnormal neurological findings reflecting involvement of the dominant parietal lobe when they occur in isolation. In clinical practice the four features that Gerstmann described almost invariably occur in association with visual and speech disturbance. A simple way to remember this is to recall the abbreviation for the Royal Australian Air Force, RAAF. The abnormalities consist of:

• Right to left confusion – unable to distinguish the right from the left side

• Agraphia – inability to write

• Acalculia – inability to perform simple arithmetic (e.g. 13 – 7 = 6)

• Finger agnosia – inability to identify the correct finger.

When testing for finger agnosia the examiner asks the patient to identify the second or third digit of one hand. The side of the hand should not be tested simultaneously as this could be confused with an inability to distinguish right from left.

In most patients, many of the abnormalities described coexist. A speech disturbance is frequently associated with contralateral weakness, sensory loss or visual field disturbance.

The non-dominant hemisphere

‘LOST IN SPACE’

This is the right hemisphere in 90% of right-handed patients and 50% of left-handed patients. The simple method for remembering the abnormalities that occur in lesions of the non-dominant parietal lobe is the phrase ‘lost in space’. This consists of neglect of one side of the body, usually the left side because the right hemisphere is the non-dominant hemisphere in most patients. The patient may present with an inability to dress themselves, referred to as dressing apraxia, often only placing one arm in the sleeve of their coat, and they may neglect to shave themselves or apply makeup on one side of the face. Strictly speaking this is not true dressing apraxia, but the patient does have difficulty dressing because they are neglecting one side. Dressing apraxia where patients cannot dress themselves is a feature of dominant parietal lobe lesions. This neglect can be so severe that the patient may not be aware that their arm and leg are weak. This is referred to as anosognosia. Rarely, some patients may not even recognise the limb as their own, a condition that is called autotopagnosia. These abnormalities are often associated with visual field disturbances, visual or sensory inattention and, if the frontal lobe is involved, hemiparesis.

There are a variety of tests that can be employed to demonstrate this neglect or ‘lost in space’. These include bisecting a line, drawing a map of the country and placing the capital cities on the map or drawing a house, a bicycle, a daisy or a clock face. Invariably, one side of the illustration is not completed; some examples are shown in Figure 5.4.

FIGURE 5.4 Diagrams that patients with left-sided neglect draw The circles are usually incomplete, the numbers on a clock face or the petals on a daisy are missing down the left side and the left half of a line is neglected so that, when requested to divide the line in half, the patient draws a line through the right half of the line.

These patients present in a state of bewilderment, or they are reluctantly brought to medical attention by a concerned relative, who has noticed their erratic behaviour although they themselves are totally unaware that anything is the matter. These patients become lost in their own home. For example, when arising at night to go to the bathroom, as they walk down the hallway the bathroom is on the left-hand side of their body and is not ‘seen’. On their way back to the bedroom, they see the bathroom because it is on the right-hand side of their body, the side that they are not neglecting. Another example is a patient who suddenly cannot find their way home despite the fact that they have driven the same way home for 20 years.

The terms inattention and neglect are often confused by students. Inattention is rarely symptomatic and is elicited with bilateral simultaneous visual or sensory stimuli, while neglect can be thought of as a more severe form of inattention that results in significant symptoms and disability.

There are a number of very rare problems referred to as apraxia that may be seen in patients with parietal lobe dysfunction. Apraxia is an impairment of the ability to use objects correctly in the absence of any obvious physical disability that would prevent them from doing so. Apraxia can be elicited by requesting the patient to demonstrate how to use a toothbrush, hammer or comb [1–3]. These are described more fully at the end of this chapter.

THE OCCIPITAL LOBES

The presenting symptoms of occipital lobe pathology include:

• Visual loss. The occipital lobes are the termination of the visual pathways and are essential for visual perception and recognition. The pathways are illustrated in Figure 4.1. The fibres from the medial half of the orbit cross in the optic chiasm, and lesions of the occipital lobe will result in a congruent contralateral visual field loss termed a homonymous hemianopia. Blindness can result from bilateral occipital lobe lesions and, in these circumstances, some patients are unaware that they are blind and behave as if they can see, a condition called Anton’s syndrome or cortical blindness. The pupillary light reflexes are preserved and the eyes and fundi are normal to examination.

• Prosopagnosia. Very occasionally patients may present with prosopagnosia, which is an inability to recognise their own features in a mirror or the faces of other people. It is almost invariably associated with a visual field abnormality, usually an upper quadrantanopia.

• Visual illusions, also termed metamorphopsias, are distortions of size, form or colour. Objects may seem too small (micopsia) or too large (macropsia).

• Visual hallucinations, both unformed and formed, arise out of the occipital lobe or the junction between the occipital and temporal lobes. Formed visual hallucinations include objects, animals or people, but these may be of distorted size, either larger or smaller than normal. Unformed visual hallucinations include flashing lights, colours, stars, circles or squares and also reflect occipital lobe pathology.

THE CEREBELLUM

Disorders of the cerebellum were first characterised in the latter part of the 19th century and in the early part of the 20th century [5, 6]. Babinski recognised the impairment of rapid alternating movements and referred to this as dys- or adiadochokinesis [6].

The classic presenting features of disorders of the cerebellum include incoordination of voluntary movement (referred to as ataxia), a characteristic intention tremor (see Chapter 13, ‘Abnormal movements and difficulty walking due to central nervous system problems’) and difficulty walking due to disequilibrium and dysarthria.

• Ataxia is tested in the upper limbs by asking the patient to touch their nose and then your finger. Ensure that your finger is far enough away from the patient so that the patient has to extend their arms fully; if it is not, the patient can anchor their arm against the chest wall and disguise any ataxia. In the lower limbs ataxia is tested by asking the recumbent patient to lift their leg high up in the air and touch the examiner’s finger and then place their heel on their own kneecap. One looks for unsteadiness as the patient’s finger approaches the examiner’s finger or their nose and as the heel approaches the finger or kneecap.

• Ataxia is often examined by watching the patient slide their heel down the shin. This, however, can disguise ataxia because the patient can stabilise their leg with the heel running along the shin. Abnormalities of cerebellar function will lead to the test being performed slowly and inaccurately.

• Cerebellar function is also tested by performing rapid alternating movements. For the upper limbs this is tested by asking the patient to tap the back and then the palm of their hand on the back of their other hand. For the lower limbs the patient taps their heel up and down on the floor.

• Patients with cerebellar disorders may also develop involuntary jerking of the eyes referred to as nystagmus. This is elicited by asking the patient to look up, down and to each side.

• The dysarthria that occurs with cerebellar dysfunction is characterised by slow slurring of the speech, or speech where the words are broken up into syllables, referred to as scanning dysarthria. This latter form of dysarthria is characteristic of cerebellar pathology. Another term that is very descriptive is explosive speech because the words are at times very soft and at other times very loud.

• Difficulty walking related to cerebellar dysfunction is discussed in Chapter 12, ‘Back pain and common leg problems with or without difficulty walking’. In essence, lesions of the anterior of vermis of the cerebellum result in truncal ataxia while lesions affecting the cerebellar hemispheres cause ataxia of the limbs.

THE TEMPORAL LOBES

Patients presenting with symptoms related to temporal lobe pathology are less common than those with frontal, parietal or occipital lobe involvement. Symptoms include:

• fluent dysphasia

• visual field defects

• auditory, visual, olfactory and gustatory hallucinations

• memory problems.

The disorder of speech has been discussed earlier in this chapter. The visual field defect is a contralateral homonymous upper quadrantanopia. The various hallucinations are discussed in Chapter 8, ‘Seizures and epilepsy’. Although the temporal lobes are involved with vestibular function, vertigo is only rarely seen with temporal lobe pathology; it may be the aura of a seizure (see Chapter 8).

TESTING HIGHER COGNITIVE FUNCTION

Higher cognitive function (HCF) consists of memory, orientation, concentration, language, stimulus recognition (examined by tests for agnosia), and performance of learned skilled movements (examined by tests for apraxia). Agnosia is the inability to recognise sensory stimuli and apraxia is the inability to use objects properly [4].

The Mini-Mental State Examination

The Mini-Mental State Examination [9] is a standardised, widely accepted test that is used to screen for cognitive impairment. It examines orientation in some detail and then briefly touches on registration and recall, attention/concentration, language and constructional abilities. It consists of 11 questions and can be administered in 5–10 minutes. This is a screening test that may indicate a need for more extensive testing. Details are given in Appendix A.