Neurology - Cranial nerves

Question 1

Optic nerve (CN II) clinical testing

Answer 1

light reflexes, visual field testing, Snellen chart

Question 2

Oculomotor nerve (CN III) clinical testing

Answer 2

Extraocular eye movements (all except down & in and lateral gaze)

Question 3

Trochlear nerve (CN IV) clinical testing

Answer 3

extraocular eye movements (down & In)

Question 4

Trigeminal nerve (CN V) clinical testing

Answer 4

facial sensations, power of muscles of mastication

Sensory

1. Ask patient to close their eyes
2. Gently brush the skin in each dermatome with a fine tip of cotton wool
3. Ask the patient to tell you when they feel their skin being touched
4. Compare the two sides

Motor

1. Palpate the strength of contraction of the masseter and temporalis by asking the patient to clench their teeth
2. Ask patient to open their jaw again resistance

Question 5

Abducent (CN VI) clinical testing

Answer 5

extraocular eye movements (lateral gaze)

Question 6

Facial (CN VII) clinical testing

Answer 6

power of muscles of facial expression

ask patient to frown, close eyes tightly and smile

Question 7

Vestibulocochlear (CN VIII) clinical testing

Answer 7

Rhinne’s and Weber’s hearing tests

Question 8

Which cranial nerves are not routinely tested?

Answer 8

Olfactory CN I and Glossopharyngeal CN IX

Question 9

Vagus nerve (CN X) clinical testing

Answer 9

Elevation of soft palate, normal swallow and speech

• ask patient to say ‘ah’ – also tests CNV3
• motor function
• uvula should lift straight up in midline
• unilateral pathology will pull uvula away from the non-functioning side
• ask patient to swallow small amount of water
• watch larynx movement
• splutter may suggest abnormal swallow
• listen to speech
• hoarseness may suggest abnormal function of muscles of larynx
• ask patient to cough
• remember also requires diaphragm

Question 10

Spinal Accessory Nerve (CN XI) clinical testing

Answer 10

ask patient to shrug shoulders

ask them to turn head to look up towards the opposite side

Question 11

Hypoglossal NErve (CN XII) clinical testing

Answer 11

ask patient to stick tongue straight out
if both CNXII’s are functioning normally the tongue tip remains in the midline on protrusion
if there is unilateral CN XII pathology the tongue tip will point towards the side of the injured nerve