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stimuli at the points marked, both the dermatomal and main peripheral nerve distributions are tested simultaneously. A Anterior view. B Posterior view.

may also be autonomic involvement, causing symptoms affecting

sweating, sphincter control and the cardiovascular system (such

as orthostatic hypotension). In mononeuritis multiplex, different

nerves in the upper and lower limbs can be affected in a stepwise

fashion.

In ‘large-fibre’ neuropathies, such as Guillain–Barré syndrome,

vibration and joint position sense may be disproportionately

affected (reduced vibration sense at the ankle may be normal in

people over 60 years). Patients may report staggering when they

close their eyes during hair washing or in the dark (Romberg’s

sign, p. 135). When joint position sense is affected in the arms,

pseudoathetosis may be demonstrated by asking the patient to

close their eyes and hold their hands outstretched; the fingers/arms

will make involuntary, slow, wandering movements, mimicking

athetosis. Interpretation of sensory signs requires knowledge of

the relevant anatomy of sensory nerves and dermatomes (Figs

7.26 and 7.27). In ‘small-fibre’ neuropathies, in which pain and

temperature sensation are mainly affected, the only finding may

be reduced pinprick and temperature sensation; there may also

be autonomic involvement. The most common causes worldwide

are diabetes mellitus and HIV infection.

Spinal cord

Traumatic and compressive spinal cord lesions cause loss or

impairment of sensation in a dermatomal distribution below the

level of the lesion. A zone of hyperaesthesia may be found in

the dermatomes immediately above the level of sensory loss.

Syringomyelia (a fluid-filled cavity within the spinal cord) can

result in a dissociated pattern of altered spinothalamic (pain

and temperature) sensation and motor function, with sparing

of dorsal column (touch and vibration) sensation.

When one-half of the spinal cord is damaged, the Brown–

Séquard syndrome may occur. This is characterised by ipsilateral

upper motor neurone weakness and loss of touch, vibration and

joint position sense, with contralateral loss of pain and temperature

(see Fig. 7.25B).

Intracranial lesions

Brainstem lesions are often vascular, and you must understand

the relevant anatomy to determine the site of the lesion. Lower

brainstem lesions may cause ipsilateral numbness on one side

146 • The nervous system

Examination sequence

• Look for wasting of the thenar eminence.

• Test thumb abduction with the patient’s hand held

palm up on a flat surface. Ask the patient to move their

thumb vertically against your resistance (abductor pollicis

brevis).

• Test opposition by asking the patient to touch their thumb

and ring finger together while you attempt to pull them

apart (opponens pollicis).

• Test for altered sensation over the hand involving the

thumb, index and middle fingers and the lateral half

of the ring finger – splitting of the ring finger (see

Fig. 7.27A).

• Tinel’s sign is elicited by tapping the distal wrist crease

with the tendon hammer, which may produce tingling in

the median nerve territory. Although often used, it has

poor sensitivity and specificity.

• Phalen’s test is forced flexion of the wrist for up to 60

seconds, to induce symptoms; it also has limited

sensitivity and specificity.

Radial nerve

This may be compressed as it runs through the axilla, in the

spiral groove of the humerus (Saturday night palsy), or may be

injured in fractures of the humerus. It typically causes wrist drop.

Examination sequence

• Test for weakness of brachioradialis (elbow flexor) and the

extensors of the arm (triceps), wrist and fingers.

• Look for sensory loss over the dorsum of the hand (see

Fig. 7.27B) and loss of triceps tendon jerk.

Ulnar nerve

The ulnar nerve is most often affected at the elbow by external

compression as the nerve is exposed, or by injury, as in elbow

dislocation/fracture. Compression usually occurs as the nerve

passes through the condylar groove behind the medial epicondyle

of the humerus or as it passes through the cubital tunnel.

of the face (V nerve nucleus) and contralateral body numbness

(spinothalamic tract).

Thalamic lesions may cause patchy sensory impairment on

the opposite side with unpleasant, poorly localised pain, often

of a burning quality.

Cortical parietal lobe lesions typically cause sensory inattention

but may also affect joint position sense, two-point discrimination,

stereognosis (tactile recognition) and localisation of point touch.

Two-point discrimination and touch localisation are not helpful

signs and tests are not performed routinely.

Peripheral nerves

Peripheral nerves may be damaged individually (mononeuropathy)

or multiply (peripheral neuropathy or mononeuritis multiplex).

Certain nerves (median nerve at the wrist, common peroneal

nerve at the knee) are particularly prone to compression.

Median nerve

The medial nerve may be compressed as it passes between the

flexor retinaculum and the carpal bones at the wrist (carpal tunnel

syndrome). This is the most common entrapment neuropathy

and initially produces sensory symptoms and pain in the hands,

occasionally radiating up the arm – typically at night. Carpal

tunnel syndrome occurs commonly during pregnancy (Box 7.11).

7.11 Common features of carpal tunnel syndrome

• It is more common in women

• There is unpleasant tingling in the hand

• It may not observe anatomical boundaries, radiating up the arm to

the shoulder

• Weakness is uncommon; if it does occur, it affects thumb abduction

• Symptoms are frequently present at night, waking the patient from

sleep

• The patient may hang the hand and arm out of the bed for relief

• There is thenar muscle wasting (in longstanding cases)

• It is commonly associated with pregnancy, diabetes and

hypothyroidism

Fig. 7.27 Sensory and motor deficits in nerve lesions. A Median. B Radial. C Ulnar. D Common peroneal. E Lateral cutaneous of the thigh.

Investigations • 147

(for example, syncope versus seizure; see Box 7.2), and also

epidemiology (sudden-onset leg weakness in a 72-year-old man

with diabetes and previous angina is unlikely to have the same

explanation as a new foot drop in a 20-year-old carpet fitter).

Draw up a differential diagnosis and then consider which (if any)

investigations are pertinent. Sometimes during the summarising

process it may become clear that there are aspects of the history

that have not been adequately addressed. Go back and resolve

these areas. Time spent reviewing the history is never wasted;

undertaking unnecessary tests, on the other hand, is more than

just a waste of time.

Do not place undue emphasis on an isolated sign that fails

to fit with the history, such as an apparently isolated extensor

plantar response in a patient with typical migraine. It is more

likely that this is a false-positive sign due to an inept examination/

interpretation of a ticklish patient rather than an indication of

underlying pathology.

Investigations

Initial investigations

Not all patients require investigation. Most patients with headache,

for example, need no tests, but some do (such as a 75-yearold man with new-onset headache and temporal tenderness

on examination, who should have urgent measurement of

the erythrocyte sedimentation rate and C-reactive protein

and a temporal artery biopsy). Unfortunately, the increasing

availability of tests means that many patients are investigated

unnecessarily, which creates new problems (such as what to

do with the unexpected, and quite incidental, finding of an

unruptured intracranial aneurysm identified in a patient with

migraine). Avoid doing tests because you can or because you

do not know what else to do. Magnetic resonance imaging

(MRI) of the brain may unearth incidental findings of no clinical

relevance in up to 20%, depending on age, and there is an

irony – usually lost on your patient – in attempting reassurance

with a scan only to identify an incidental ‘abnormality’. Sometimes

a single carefully chosen test is all that is necessary to confirm a

diagnosis. For example, a patient with chorea, whose father died

of Huntington’s disease, will almost certainly have the diagnosis

confirmed with genetic testing, without the need for imaging or

other tests.

Consider your diagnosis and start with any necessary simple

blood tests (such as exclusion of metabolic disturbance, including

diabetes); then work upwards. If imaging is required, decide

what to image using which modality (computed tomography,

MRI, ultrasound or functional imaging), and whether any special

sequences or techniques are necessary (like intravenous contrast;

Figs 7.28–7.30). Discuss the case with the radiologists if you

are unsure. For some PNS disorders, nerve conduction studies

and electromyography may be helpful. Electroencephalography

is perhaps the most misused test in neurology. Think carefully

about whether it will add anything to what you already know;

it should not be used to diagnose epilepsy. The more invasive

tests (lumbar puncture, nerve/muscle/brain biopsy) all require

careful consideration and should be guided by specialists.

Lastly, the worlds of antibody-mediated and genetic diseases

are changing rapidly, and you may need to have a discussion with

the relevant experts about which specialised test might be most

appropriate.

Examination sequence

• Examine the medial elbow, palpating the nerve in the ulnar

groove (the most common place of entrapment). Note any

scars or other signs of trauma.

• Look for wasting of the interossei (dorsal guttering).

• Test for weakness of finger abduction with the patient’s

fingers on a flat surface, and ask them to spread the

fingers against resistance from your fingers.

• Test adduction by asking them to grip a card placed

between their fingers and pulling it out using your own

fingers.

• Assess for sensory loss on the ulnar side of the hand,

splitting the ring finger (see Fig. 7.27C).

Common peroneal nerve

The nerve may be damaged by fractures as it winds around

the fibular head, or it may be compressed, particularly in thin,

immobile patients or as a result of repetitive kneeling, squatting

or sitting with the legs crossed at the knees. It typically causes

a foot drop.

Examination sequence

• Test for weakness of ankle dorsiflexion and eversion;

test for extension of the big toe (extensor hallucis

longus). Inversion and the ankle reflex will be

preserved.

• Test for sensory loss over the dorsum of the foot (see

Fig. 7.27D).

Lateral cutaneous nerve of the thigh

This purely sensory nerve may be compressed as it passes

under the inguinal ligament, producing paraesthesiae in the lateral

thigh (meralgia paraesthetica, which means burning numbness)

(see Fig. 7.27E).

Examination sequence

• Ask the patient to map out the area of disturbance.

• Test for disturbed sensation over the lateral aspect of the

thigh. Palpate the abdomen and groin for masses or

inguinal lymph nodes.

Interpretation of the findings

Having completed the history and examination, first decide

whether the symptoms are due to neurological disease, a

functional neurological disorder or non-neurological causes. Try

to localise the lesion to a single area of the nervous system if

possible (Is the lesion in the CNS or PNS?) and then localise in

more detail (for example: If the lesion is in the PNS, is it in the

root, nerves or neuromuscular junction muscle?). Some conditions,

like multiple sclerosis, may give rise to multiple symptoms and

signs because they involve several lesions; others, like migraine

or functional disorders, do not follow strict neurological and

anatomical rules.

Having localised the lesion, consider the likely underlying

pathology (What is the lesion?). This will depend on the history

148 • The nervous system

A B C

Fig. 7.28 Imaging of the head. A DaTscan showing uptake of tracer (dopamine receptors) in the basal ganglia on cross-section of the brain.

B Magnetic resonance scan showing ischaemic stroke. T2 imaging demonstrates bilateral occipital infarction and bilateral hemisphere lacunar infarction.

C Unenhanced computed tomogram showing subarachnoid blood in both Sylvian fissures (white arrows) and early hydrocephalus. The temporal horns of

the lateral ventricles are visible (black arrows).

A B C

Fig. 7.29 Imaging of the head. A Computed tomogram (CT) showing a cerebral abscess. B Magnetic resonance scan showing multiple sclerosis with

white demyelinating plaques. C CT scan showing a large meningioma arising from the olfactory groove.

A B

Fig. 7.30 T2 magnetic resonance images showing a large left paracentral L4–5 disc protrusion (arrowed) compressing the L5 nerve root.

A Sagittal section. B Axial section.

Investigations • 149

Specific investigations

Lumbar puncture

Lumbar puncture is a key investigation in a number of acute and

chronic neurological conditions. Always measure the CSF opening

pressure (in a lying position, not sitting), using an atraumatic (blunt)

needle. CSF is routinely examined for cells, protein content and

glucose (compared to simultaneously taken blood glucose); it is

also stained and cultured for bacteria. Other specific tests may be

carried out, such as analysis for oligoclonal bands, meningococcal

and pneumococcal antigens, polymerase chain reaction (PCR)

for certain viruses or cytology for malignant cells.

Neurophysiological tests

Electroencephalography (EEG) records spontaneous electrical

activity of the brain, using scalp electrodes. It is employed in

OSCE example 1: Headache history

Miss Bolton, 32 years old, presents acutely with a severe global headache, associated with vomiting and feeling dreadful.

Please take a history from this patient

Confirm:

• Onset – gradual or sudden.

• Site – lateralised or global.

• Severity.

• Aggravating and relieving factors, such as bright light.

• Associated symptoms, such as vomiting, photophobia, neck pain, visual disturbance.

• Relevant family history.

Summarise your findings

This 32-year-old woman’s headache began gradually last night and is worse today; she has been in bed in a darkened room, trying to sleep. She has

vomited the analgesia she took. She often has headaches at the time of her period but this is the worst headache she has ever experienced. She

recalls having one or two migraines as a child, and her mother had migraine. She is otherwise well and takes no medication other than the oral

contraceptive. The examination is normal, although she looks tired and distressed.

Suggest a differential diagnosis

The most likely diagnosis is migraine; the headache evolved and worsened over a few hours, with no ‘red flags’, on a background of a predisposition

to migraine. The differential includes more sinister causes such as meningitis, cerebral venous sinus thrombosis or intracranial haemorrhage, but there

are no features to support these. The headache is likely to resolve in the next day or two.

Suggest initial investigations

She does not need any tests, as there are no features to suggest she needs brain imaging or lumbar puncture to exclude a subarachnoid haemorrhage

or meningitis.

the investigation of epilepsy, encephalopathies or dementia.

Modifications to standard EEG improve sensitivity and include

sleep-deprived studies, prolonged videotelemetry and invasive

EEG monitoring.

Electromyography (EMG) involves needle electrodes inserted

into muscle. Electrical activity is displayed on an oscilloscope

and an audio monitor, allowing the neurophysiologist to see and

hear the pattern of activity. Neurogenic and myopathic pathology

causes characteristic EMG abnormalities.

Nerve conduction studies involve applying electrical stimuli

to nerves and measuring the speed of impulse conduction.

They are used for both motor and sensory nerves, and are

helpful in diagnosing peripheral nerve disorders such as nerve

compressions or polyneuropathies. They are also helpful is

distinguishing between axonal and demyelinating neuropathies,

the underlying causes and management of which are very

different.

OSCE example 2: Tremor

Mr Anderson, 76 years old, presents with a tremor of his arm.

Please examine his arms

• Introduce yourself and clean your hands.

• Observe the patient sitting at rest; note any tremor, abnormal postures, facial expression, jaw/chin tremor, drooling.

• Listen to his speech.

• Ask him to raise both arms above his head, then to stretch them out in front of him; observe any tremor on posture.

• Ask him to perform piano-playing movements; look carefully for asymmetry and reduced fine finger movements.

• Assess tone, looking specifically for asymmetry, and cog wheeling or lead pipe rigidity in the affected right arm.

• Test power in shoulder abduction, elbow flexion/extension and finger extension.

• Test upper limb deep tendon reflexes (biceps, supinator and triceps).

• Omit sensory testing, as this is unlikely to add anything.

• Test finger-to-nose movements.

• Ask him to walk, observing what happens to the tremor and right arm swing.

• Thank the patient and clean your hands.

Continued

150 • The nervous system

Integrated examination sequence for the nervous system

A complete neurological examination is demanding for both doctor and patient, and in many cases will not be necessary. The history will dictate a

more targeted examination, and time spent on the history is always more productive than an amateur neurological examination.

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Sunday, October 9, 2022

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