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81Neurology

Station 32

Cranial nerve examination

Specifications: You may be asked to limit your examination to certain cranial nerves only, e.g. I–VI,

VII–XII.

Before starting

• Introduce yourself to the patient.

• Confirm his name and date of birth.

• Explain the examination and obtain his consent.

• Ensure that he is comfortable.

The examination

The olfactory nerve (CN I)

• Ask the patient if he has noticed a change in his sense of smell or taste. If he has, indicate that

you would perform an olfactory examination by asking him to smell different scents, such as

mint or coffee. Otherwise, the olfactory nerve is not formally tested.

The optic nerve (CN II)

(See Station 51: Vision and the eye examination for more details.)

• Ask the patient whether he wears glasses. If he does, ask him to put them on.

• Ask about any changes in vision and the time frame over which they have occurred. Use the

mnemonic AFRO C (Acuity, Fields, Reflexes, Ophthalmoscopy/Fundoscopy, and Colour vision)

to guide you through the following steps.

• Acuity: Use a Snellen chart from a distance of 6 metres and test near vision by asking the patient

to read test types (or a page in a book).

• Fields: Sit directly opposite the patient, at the same level as him. Ask him to look straight at

you and to cover his right eye with his right hand. Cover your left eye with your left hand, and

test the visual field of his left eye with your right hand. Bring a wiggly finger into the upper left

quadrant, asking the patient to say when he sees the finger. Repeat for the lower left quadrant.

Then swap hands and test the upper and lower right quadrants. Now ask the patient to cover

his left eye with his left hand. Cover your right eye with your right hand and test the visual field

of his right eye with your left hand. Bring a wiggly finger into the upper right quadrant, asking

the patient to say when he sees the finger. Repeat for the lower right quadrant. Then swap

hands and test the upper and lower left quadrants.

• Indicate that you could use a red hat pin to uncover the blind spot and the presence of a central

scotoma.

• Reflexes: See under CN III, IV and VI testing.

• Indicate that you could examine the eyes by direct ophthalmoscopy/fundoscopy.

• Indicate that you could test red/green colour vision with Ishihara plates.

Clinical Skills for OSCEs

82 Station 32 Cranial nerve examination

Figure 22. Visual field defects and their origins.

The oculomotor, trochlear, and abducens nerves (CN III, IV, and VI)

(See Station 51: Vision and the eye examination for more details.)

• Inspect the eyes, paying particular attention to the size and symmetry of the pupils, and excluding a visible ptosis (Horner’s syndrome) or squint.

• Test the direct and consensual pupillary light reflexes. Explain that you are going to shine a

bright light into the patient’s eye and that this may feel uncomfortable. Bring the light in onto

his left eye and look for pupil constriction. Bring the light in onto his left eye once again, but

this time look for pupil constriction in his right eye (consensual reflex). Repeat for the right eye.

• Perform the swinging flashlight test to detect a relative afferent pupillary defect. Swing the light

from one eye to another and look for sustained pupil constriction in both eyes. Intermittent

pupil constriction in one eye (Marcus Gunn pupil) suggests a lesion of the optic nerve anterior

to the optic chiasm.

• Perform the cover test. Ask the patient to fixate on a point and cover one eye. Observe the

movement of the uncovered eye. Repeat the test for the other eye.

• Examine eye movements. Ask the patient to keep his head still and to follow your finger with

his eyes. Ask him to report any pain or double vision at any point. Draw an ‘H’ shape with your

finger. Observe for nystagmus at the extremes of gaze.

• Test the accommodation reflex. Ask the patient to follow your finger in to his nose. As the eyes

converge, the pupils should constrict.

Optic

radiation

Lateral

geniculate

body

Optic

tract

Optic

chiasm

Left Right

Left eye

 Loss of vision

1

2

3

4

5

6

Right eye

Optic

nerve

5

6

3

4

2

1

Neurology

Station 32 Cranial nerve examination 83

The trigeminal nerve (CN V)

Sensory part

• Using cotton wool, test light touch in the three branches of the trigeminal nerve. Compare

both sides.

• Indicate that you could test the corneal reflex, but that this is likely to cause the patient some

discomfort.

Motor part

• Test the muscles of mastication (the temporalis, masseter, and pterygoid muscles) by asking

the patient to:

– clench his teeth (palpate his temporalis and masseter muscles bilaterally)

– open and close his mouth against resistance (place your fist under his chin)

• Indicate that you could test the jaw jerk. Ask the patient to let his mouth fall open slightly. Place

your fingers on the top of his mandible and tap them lightly with a tendon hammer.

The facial nerve (CN VII)

• Look for facial asymmetry. Note that the nasolabial folds and the angle of the mouth are especially indicative of facial asymmetry.

Sensory part

• Indicate that you could test the anterior two-thirds of the tongue for taste.

Motor part

• Test the muscles of facial expression by asking the patient to:

– lift his eyebrows as far as they will go

– close his eyes as tightly as possible (try to open them)

– blow out his cheeks

– purse his lips or whistle

– show his teeth

Ophthalmic

branch

Maxillary

branch

Mandibular

branch

Gasserian

ganglion

Trigeminal

nerve

Figure 23. The three branches

of the trigeminal nerve.

‘Trigeminal’ means ‘three twins’.

Clinical Skills for OSCEs

84 Station 32 Cranial nerve examination

The acoustic nerve (CN VIII)

(See Station 52: Hearing and the ear examination for more details.)

• Test hearing sensitivity in each ear by occluding one ear and rubbing your thumb and fingers

together in front of the other.

• Indicate that you could carry out the Rinne and Weber tests and examine the ears by auroscopy

(see Station 52).

The glossopharyngeal nerve (CN IX)

• Indicate that you could test the gag reflex by touching the tonsillar fossae on both sides with a

tongue depressor, but that this is likely to cause the patient some discomfort.

The vagus nerve (CN X)

• Ask the patient to phonate (say ‘aah’) and, aided by a pen torch, look for deviation of the uvula

to the opposite side of the lesion. Use a tongue depressor if necessary.

The hypoglossal nerve (CN XII)

• Aided by a pen torch, inspect the tongue for wasting and fasciculation.

• Ask the patient to stick out his tongue and look for deviation to the side of the lesion. Now ask

him to wiggle it from side to side.

The accessory nerve (CN XI)

• Look for wasting of the sternocleidomastoid and trapezius muscles.

• Ask the patient to:

– shrug his shoulders against resistance

– turn his head to either side against resistance

After the examination

• Thank the patient.

• Ensure that he is comfortable.

• If appropriate, state that you would order some key investigations, e.g. a CT or MRI.

• Summarise your findings and offer a differential diagnosis.

Conditions most likely to come up in a cranial nerve examination station

Third nerve palsy:

• the eye is depressed and abducted (down and out).

• elevation, adduction, and depression are limited, but abduction and intortion are normal.

• there is a ptosis (drooping of the upper eyelid).

• the pupil may be dilated and unreactive to light or accommodation.

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Station 32 Cranial nerve examination 85

Bell’s (facial nerve) palsy:

• facial drooping and paralysis on the affected half.

• if the forehead muscles are spared, it is a central rather than a peripheral palsy.

Horner’s syndrome:

• signs of Horner’s syndrome are ptosis, miosis, enophthalmos, and facial anhidrosis.

Cavernous sinus syndrome:

• the cavernous sinus contains the carotid artery and its sympathetic plexus, CN III, IV, and VI,

and the ophthalmic and maxillary branches of CN V.

• signs of a cavernous sinus lesion may include (generally unilateral) proptosis, chemosis,

ophthalmoplegia, and loss of sensation in the first and second divisions of the trigeminal

nerve.

Cerebellopontine angle syndrome:

• lesions in the area of the cerebellopontine angle can cause compression of CN V, VII, and VIII.

• signs may include palsies of CN V and VII, nystagmus, ipsilateral deafness, and ipsilateral

cerebellar signs.

Bulbar palsy:

• lower motor neurone lesion in the medulla oblongata leads to bilateral impairment of

function of CN IX–XII.

• signs include speech difficulties, dysphagia, wasting and fasciculation of the tongue, absent

palatal movements, absent gag reflex.

Pseudo-bulbar palsy:

• upper motor neurone lesion in the corticobulbar pathways in the pyramidal tract leads to

impairment of function of CN IX–XII and also CN V and VII.

• signs include speech difficulties, dysphagia, conical and spastic tongue, brisk jaw jerk,

emotional lability.

Clinical Skills for OSCEs

86 Station 33

Motor system of the upper limbs examination

Before starting

• Introduce yourself to the patient.

• Confirm his name and date of birth.

• Explain the examination and obtain his consent.

• Position him and ask him to expose his arms completely.

• Ask if he is currently experiencing any pain.

The examination

Inspection

• Look for abnormal posturing.

• Look for abnormal movements such as tremor, fasciculation, dystonia, athetosis.

• Assess the muscles of the hands, arms, and shoulder girdle for size, shape, and symmetry. You

can also measure the circumference of the arms.

Tone

• Ensure that the patient is not in any pain.

• Ask the patient to relax the muscles in his arms.

• Test the tone in the upper limbs by holding the patient’s hand and simultaneously pronating

and supinating and flexing and extending the forearm. If you suspect increased tone, ask the

patient to clench his teeth and re-test. Is the increased tone best described as spasticity (claspknife) or as rigidity (lead pipe)? Spasticity suggests a pyramidal lesion, rigidity suggests an

extra-pyramidal lesion.

Power

• Test muscle strength for shoulder abduction, elbow flexion and extension, wrist flexion and

extension, finger flexion, extension, abduction, and adduction, and thumb abduction and opposition. Compare muscle strength on both sides, and grade it on the MRC muscle strength scale:

0 No movement.

1 Feeble contractions.

2 Movement, but not against gravity.

3 Movement against gravity, but not against resistance.

4 Movement against resistance, but not to full strength.

5 Full strength.

Table 13. Important root values in the upper limb – muscle strength

• Shoulder abduction C5

• Elbow flexion C6

• Elbow extension C7

• Wrist extension C6, C7

• Wrist flexion C7, C8

• Finger extension C7 (radial nerve)

• Finger flexion C8

• Finger abduction/adduction T1 (ulnar nerve)

• Thumb abduction/opposition T1 (median nerve)

Neurology

Station 33 Motor system of the upper limbs examination 87

Reflexes

• Test biceps, supinator, and triceps reflexes with a tendon hammer (see Figure 24). Compare both

sides. If an upper limb reflex cannot be elicited, ask the patient to clench his teeth and re-test.

Table 14. Important root values

in the upper limb – reflexes

• Biceps C5, C6

• Supinator C6

• Triceps C7

Figure 24. Testing (A) biceps, (B) supinator, and (C) triceps

reflexes.

Cerebellar signs

• Test for intention tremor, dysynergia, and dysmetria (past-pointing) by asking the patient to

carry out the finger-to-nose test.

– place your index finger at about 2 feet from the patient’s face. Ask him to touch the tip of his

nose and then the tip of your finger with the tip of his index finger. Once he is able to do this,

ask him to do it as fast as he can. And remember that he has two hands!

• Then test for dysdiadochokinesis.

– ask the patient to clap and then show him how to clap by alternating the palmar and dorsal

surfaces of one hand. Once he is able to do this, ask him to do it as fast as he can. Ask him to

repeat the test with his other hand

(A)

(B)

(A)

(B)

(C)

Clinical Skills for OSCEs

88 Station 33 Motor system of the upper limbs examination

After the examination

• Thank the patient.

• Ensure that he is comfortable.

• Ask to carry out a full neurological examination.

• If appropriate, indicate that you would order some key investigations, e.g. CT, MRI, nerve conduction studies, electromyography, etc.

• Summarise your findings and offer a differential diagnosis.

Conditions most likely to come up in a motor system of the upper limbs examination station

Parkinson’s disease:

• motor signs include forward-flexed posture, mask-like facial expression, speech difficulties,

resting tremor, cogwheel rigidity, bradykinesia.

Cerebellar lesion:

• motor signs depend on the anatomy of the lesion, and may include nystagmus, slurred

or staccato speech, hypotonia, hyporeflexia, intention tremor, dysmetria, dysynergia,

dysdiadochokinesis, ataxia.

Ulnar nerve lesion:

• wasting, weakness, numbness, and tingling in the fifth finger and in the medial half of the

fourth finger.

• curling up of the fifth and fourth fingers (‘ulnar claw’) indicates that the nerve is severely

affected.

Median nerve lesion:

• a lesion at the level of the wrist produces wasting of the thenar muscles, weakness of

abduction and opposition of the thumb, and numbness over the palmar aspect of the thumb,

index finger, third finger, and lateral half of the fourth finger.

• a lesion at the level of the forearm produces additional weakness of flexion of the distal and

middle phalanges.

• a lesion at the   level of the elbow or above produces additional weakness of pronation of the

forearm and ulnar deviation of the wrist on wrist flexion.

Radial nerve lesion:

• a lesion at the level of the axilla or above produces weakness of elbow extension and flexion,

weakness of wrist and finger extension with attending wrist drop and finger drop, weakness of

thumb abduction and extension, and sensory loss over the dorsoradial aspect of the hand and

the dorsal aspect of the radial 3½ fingers (usually circumscribed to a small, triangular area over

the first dorsal web space).

• inferior lesions are likely to spare triceps (elbow extension), brachioradialis (elbow flexion),

and extensor carpi radialis longus (wrist extension and radial abduction, but this muscle is

only one of five wrist extensors).

Radiculopathy, affecting a single root nerve (see Table 14)

Hemiplegia/hemiparesis:

• paralysis or weakness on one side of the body accompanied by decreased movement control,

spasticity, and hyper-reflexia (upper motor neurone syndrome).

Myopathy:

• symmetrical weakness predominantly affecting proximal muscle groups.

• in contrast to neuropathy, in myopathy muscle atrophy and hyporeflexia occur very late.