Cranial nerve examination

Question 1

Olfactory nerve function

Answer 1

Conveys sense of smell

Question 2

Optic nerve function

Answer 2

Conveys vision

Question 3

Oculomotor nerve function

Answer 3

Innervates superior, medial and inferior rectus muscles, inferior oblique and levator palpebrae superioris muscles. Also parasympathetic innervation of constrictor pupilae and ciliary muscle.

Question 4

Trochlear nerve function

Answer 4

Innervates the superior oblique muscle of the eye.

Question 5

Trigeminal nerve function

Answer 5

Supplies sensation to face, and motor function to muscles of mastication.

Question 6

Abducens nerve function

Answer 6

Innervated lateral rectus muscle.

Question 7

Facial nerve function

Answer 7

Supplies muscles of facial expression.

Also taste to anterior 2/3 of tongue and secretomotor to submandibular and sublingual glands.

Question 8

Vestibulocholear nerve function

Answer 8

Vestibular - equilibrium and balance

Cochlear - hearing

Question 9

Glossopharyngeal nerve function

Answer 9

Glossopharyngeal nerve carries sensation from the pharynx and tonsils, and sensation and taste from the posterior 1/3 of the tongue, and innervates stylopharyngeus muscles.

Question 10

Vagus nerve function

Answer 10

Vagus nerve carries sensation and innervates paletine, pharyngeal and laryngeal muscles.

Question 11

Accessory nerve function

Answer 11

Innervates upper trapezius and sternocleidomastoid

Question 12

Hypoglosssal nerve function

Answer 12

Innervated muscles of the tongue

Question 13

How to test olfactory nerve

Answer 13

• Ask about any changes in sense of smell. If present, is it unilateral or bilateral?
• Can test each nostril separately using a strong smelling substance like soap or coffee.

Question 14

How to test optic nerve

Answer 14

• Visual acuity - Snellen chrart, one eye at a time
• Pupillary responses - Inspect size and shape of pupil, checking for symmetry, then the pupillary response to light
• Visual fields
• VIsual inattention

Question 15

How to test occulomotor, trochlear and abducens nerve

Answer 15

• Inspect eyes, looking for pupil abnormality, presence of ptosis (drooping of eyelid) or any abnormality of gaze.
• Ask the patient to keep their head still. Ask them to follow your finger as it moves in a slow ‘H’. Start in the midline directly in front of the patient. Ask the patient to tell you if they get any double vision. Note if their eyes always move in parallel. Look for nystagmus, particularly at the extremes of eye movement.

Question 16

How to test trigeminal nerve

Answer 16

• Sensation - Using a piece of cotton wool (eyes closed), then the sharp end of a Neurotip (eyes can be open), touch the ophthalmic (forehead, V1), maxillary (cheek, V2) and mandibular (lower jaw, V3) areas.
• Motor (V3) - Palpate the bulk of the masseter muscle and then ask the patient to clench their teeth. Ask patient to open jaw against resistance to test pterygoid muscles.
• Corneal reflex - (afferent V1 & efferent CN VII):
  Ask the patient to look up to the left and touch the cornea of the right eye on the lateral side with a wisp of cotton wool. Look for a blink response, which should be bilateral.
• Jaw jerk reflex - This reflex is normally absent/slight but may be pronounced if an UMN lesion is present.

Question 17

How to test facial nerve

Answer 17

• Inspection - Inspect the face for any asymmetry.
• Motor - Look at facial movement, asking the patient to wrinkle their forehead, then screw up their eyes, and then smile/show their teeth. Ask the patient to puff out their cheeks, then press gently on their cheeks to try to expel air.
• Sensation - Taste sensation is rarely tested.

Question 18

How to test vestibulochoclear nerve

Answer 18

• Vestibular - Check for nystagmus (NB In practice, this is usually done when testing eye movements). Check balance (this is often done when testing gait).
• Hearing - Whisper test, Tuning fork tests: Rinne’s and Webber’s

Question 19

How to test glossopharyngeal and vagus nerve

Answer 19

• Inspection - Ask the patient to open the mouth and say “Aah”. Look to see if the palate moves symmetrically. Normally both sides of the palate elevate and the uvula should remain central.
• Cough - Ask the patient to cough and hear if this sounds normal. (afferent – IX, efferent - X)
• Gag reflex - touch the side of the throat (in the region of the fauces) on each side, one at a time, and look for reflex contraction of the pharyngeal muscles.

Question 20

How to test accessory nerve

Answer 20

• Trapezius - Place your hands on the patient’s shoulders and then ask the patient to shrug their shoulders. Look at and feel the contraction of the trapezius muscles.
• Sternocleidomastoid - Ask the patient to turn their head to one side, so that you can see the contralateral muscle contract. The patient should then push against the side of your fist with their face.

Question 21

How to test hypoglossal nerve

Answer 21

• Inspection - Ask the patient to open their mouth. Look at the tongue at rest for fasciculation, wasting or deviation.
• Motor - Then ask the patient to stick out their tongue and move it from side to side.
• Speech - This is a good opportunity to test speech, particularly if you haven’t heard the patient speak already (e.g. ask them to say the days of the week).