use a

wisp of cotton wool (or lightly apply your finger) and ask

the patient to say ‘yes’ to each touch.

• Time the stimuli irregularly and make a dabbing rather than

a stroking or tickling stimulus.

• Start distally in the feet and hands; work proximally for a

neuropathy or focus on a specific nerve distribution or

dermatome.

Superficial pain

• Use a fresh neurological pin, such as a Neurotip, not a

hypodermic needle. Dispose of the pin after each patient.

• Explain and demonstrate (on an area of skin not affected

by the lesion, such as the sternum) that the ability to feel a

sharp pinprick is being tested.

• Map out the boundaries of any area of reduced, absent or

increased sensation. Move from reduced to higher

sensibility: that is, from hypoaesthesia to normal, or normal

to hyperaesthesia.

Temperature

• Touch the patient with a cold metallic object, such as a

tuning fork, and ask if it feels cold. More sensitive

assessment requires tubes of hot and cold water at

controlled temperatures but this is seldom performed.

Vibration

Note that ankle oedema may affect perception. Strike the

tuning fork on your own palm; an average healthy person

should be able to detect the vibration this causes for over 10

seconds.

• Place a vibrating 128-Hz tuning fork over the patient’s

sternum.

• Ask the patient, ‘Do you feel it buzzing?’

• Place the fork on the patient’s big toe. If vibration is not

felt, then move it proximally to the medial malleolus; if this

is not perceived, move to the patella, then the anterior iliac

spine, lower chest wall or clavicle. Repeat on the other

(dorsal) columns of the spinal cord. Pain and temperature

sensation are carried by small, slow-conducting fibres of the

peripheral nerves and the spinothalamic tract of the spinal cord.

The posterior column remains ipsilateral from the point of entry

up to the medulla, but most pain and temperature fibres cross to

the contralateral spinothalamic tract within one or two segments

of entry to the spinal cord. All sensory fibres relay in the thalamus

before sending information to the sensory cortex in the parietal

lobe (Fig. 7.24).

Common presenting symptoms

Sensory symptoms are common and it is important to discern

what the patient is describing. Clarify that, by ‘numbness’,

Medial lemniscus

and spinothalamic

tract

Medial lemniscus

Spinothalamic tract

Spinothalamic tract

Lentiform

nucleus

Thalamus

Pain

Temperature

1/2 touch

Vibration

Position

1/2 touch

Posterior columns

(no relay)

Nucleus gracilis

Nucleus cuneatus

V nerve sensory

nucleus

Internal capsule

Caudate nucleus

Cerebral hemisphere

A

B

C T L S

Pons

Medulla

Spinal cord

Fig. 7.24 The sensory system. A Main sensory pathways.

B Spinothalamic tract: layering of the spinothalamic tract in the cervical

region. C represents fibres from cervical segments, which lie centrally;

fibres from thoracic, lumbar and sacral segments (labelled T, L and S,

respectively) lie progressively more laterally.

144 • The nervous system

Sensory inattention

• Only test if sensory pathways are otherwise intact.

• Ask the patient to close their eyes.

• Touch their arms/legs in turn and ask which side has been

touched.

• Now touch both sides simultaneously and ask

whether the left side, right side or both sides were

touched.

Sensory modalities

In addition to the modalities conveyed in the principal ascending

pathways (touch, pain, temperature, vibration and joint position

sense), sensory examination includes tests of discriminative

aspects of sensation, which may be impaired by lesions of the

sensory cortex. Assess these cortical sensory functions only if

the main pathway sensations are intact. Consider abnormalities

on sensory testing according to whether the lesion (or lesions)

is in the peripheral nerve(s), dorsal root(s) or spinal cord, or is

intracranial.

Peripheral nerve and dorsal root

Many diseases affect peripheral nerves, generally resulting

in peripheral neuropathies or polyneuropathies. Peripheral

neuropathies tend to affect the lower limbs, first starting in the

toes. In these length-dependent neuropathies the upper limbs may

become involved once the symptoms extend above the knees.

Symptoms first affecting the upper limbs suggest a demyelinating

rather than axonal neuropathy or a disease process in the nerve

roots or spinal cord. In many cases, touch and pinprick sensation

are lost in a ‘stocking-and-glove’ distribution (Fig. 7.25A). There

side. Record the level at which vibration is detected by the

patient.

• Repeat the process in the upper limb. Start at the distal

interphalangeal joint of the forefinger; if sensation is

impaired, proceed proximally to the metacarpophalangeal

joints, wrist, elbow, shoulder and finally clavicle.

• If in doubt as to the accuracy of the response, ask the

patient to close their eyes and to report when you stop

the fork vibrating with your fingers.

Joint position sense (proprioception)

• With the patient’s eyes open, demonstrate the

procedure.

• Lightly hold the distal phalanx of the patient’s great toe at

the sides. Tell the patient you are going to move their toe

up or down, demonstrating as you do so.

• Ask the patient to close their eyes and to identify the

direction of small movements in random order.

• If perception is impaired, move to more proximal joints –

ankle, knees and hips. Repeat for the other side.

• Repeat for the upper limbs. Start with movements at the

distal interphalangeal joint of the index finger; if the

movements are not accurately felt, move to the first

metacarpophalangeal joint, wrist, elbow and finally

shoulder.

Stereognosis and graphaesthesia

• Ask the patient to close their eyes.

• Place a familiar object, such as a coin or key, in their hand

and ask them to identify it (stereognosis).

• Use the blunt end of a pencil or orange stick and trace

letters or digits on the patient’s palm. Ask the patient to

identify the figure (graphaesthesia).

Distribution

of sensory

impairment

A B

Light touch causes

exquisite pain

(hyperpathia)

Impaired light touch

and vibration sense

Pyramidal weakness

Increased tendon reflexes in left

leg and extensor plantar response

Impaired pain and

temperature sense

Fig. 7.25 Patterns of sensory loss. A Length-dependent peripheral neuropathy. B Brown–Séquard syndrome. Note the distribution of corticospinal,

posterior column and lateral spinothalamic tract signs. The cord lesion is in the left half of the cord.

Sensory system • 145

7

T2

T1 T1

T2

T2

Fig. 7.26 Dermatomal and sensory peripheral map innervation. Points (shown in blue) for testing cutaneous sensation of the limbs. By applying

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.