Cranial Nerve Examination
a) Introduce yourself, obtain consent, wash your hands.
b) Position patient (they should be sitting in a chair or on the edge of a bed).
c) General inspection
Ask “Have you noticed any change in your sense of smell or taste recently?”
If yes, check that the problem is not due to a cold/blocked nose and say “I would like to formally examine the sense of smell”. This involves the use of bottles containing standard smells (rarely used) or the use of a substance with a strong aroma eg coffee. Remember to test each nostril separately.
|Acuity||Ask “Do you usually wear glasses/contact lenses?” If yes, ask patient to put them on. Use a pocket Snellen chart. “Cover your left eye with your left hand and read down the chart from the top”. Repeat for right eye. Record visual acuity. If no Snellen chart available, test using a magazine/name badge and say “I would like to formally assess acuity using a Snellen chart at 6m”
If unable to see letters, check if able to:
i) count fingers
ii) detect hand movement
iii) detect light
|Pupils||PERLA – are the Pupils Equal and Reactive to Light and Accommodation?
Inspect size and symmetry of pupils. Tell the patient that you are going to shine a light in their eyes. Shine a pen torch twice into each eye checking first for a direct and then for a consensual response (both pupils should constrict in response to a light being shone in either one of them). Dimming background light makes this process easier.
|Accommodation||Ask the patient to look at a point on the far side of the room. Then ask them to look at a point about 15cm from their face. The pupils should constrict as the patient focuses on the near object.|
|Fields||Tested by confrontation. Sit in front of, and at the same level as, the patient, about 1m apart. “Cover your right eye with your right hand please and look straight into my eye” (you should cover your left eye with your left hand at the same time). Bring a target (ideally a red hat pin, otherwise the wiggling end of your finger) in diagonally from above and below on each side (you will need to swap hands halfway through), making sure that the target is equidistant between the two of you. Ask the patient when they first see the target. Repeat for the other eye. Compare your fields with those of the patient.|
|Fundoscopy||Say “I would also like to examine the fundi with an ophthalmoscope”.|
III, IV, and VI: Oculomotor, Trochlear and Abducens
These nerves control eye movements.
Remember SO4 LR6 – CN IV supplies the superior oblique muscle, CN VI the lateral rectus, and CN III the rest (inferior oblique and the medial, inferior and superior recti).
Inspect for ptosis, squint and nystagmus.
Ask “Do you suffer from double vision?” Then go on to check eye movements. Put one hand on the patient’s chin and ask them to keep their head still and follow your finger with their eyes. Move your finger in an ‘H’ shape slowly, looking for any abnormal eye movements. Pause at the extremes of gaze to look for nystagmus. Ask the patient to report if they see double at any point.
|Motor||Test the muscles of mastication. Ask patient to clench their teeth and feel the masseters/temporalis. Ask the patient to open their jaw against resistance, and ask the patient to move their jaw from side to side against your resisting finger (pterygoids)
Offer to test the jaw jerk.
|Sensory||Test facial sensation – take a wisp of cotton wool. “Please close your eyes and tell me when you can feel me touching your face”. Test the ophthalmic, maxillary and mandibular areas. Ask the patient if the sensation feels like cotton wool. If asked, test other sensory modalities.
“At this point I would usually test the corneal reflex (afferent V, efferent VII). Warn patient. Dab the cornea gently with cotton wool, approaching from the side. The patient should blink.
Inspect – is there any asymmetry?
UMN lesion – forehead spared due to bilateral innervation (cf LMN lesion – forehead affected).
“Please raise your eyebrows”(frontalis)
“Please close your eyes tightly and stop me from opening them”(orbicularis oculi).
“Show me your teeth”(orbicularis oris)
“Puff out your cheeks” (buccinator). Try to push the air out – you shouldn’t be able to.
VIII: Auditory (aka Vestibulocochlear)
Assess hearing – rub tragus on left and whisper a number in right ear. Ask patient to repeat it. Repeat on other side.
If above test suggests hearing loss, perform Weber’s and Rinne’s tests in order to distinguish between conductive and sensorineural deficits.
Weber’s – vibrate a tuning fork. Place in the centre of the forehead. Sound should be equal in both ears. If louder on L, is either L conductive deafness or R sensorineural deafness.
Rinne’s – vibrate a tuning fork. Is the sound loudest when on mastoid process or when held in front of ear. Air conduction should be better than bone conduction.
IX, X: Glossopharyngeal and Vagus
Ask patient to open mouth. Shine in a torch and check for symmetry of palatal movement as patient says ‘aahh’.
Say “I would also like to assess the gag reflex” (afferent IX, efferent X)
Innervates trapezius and sternocleidomastoid.
Inspect for asymmetry and assess power.
“Please shrug your shoulders up and stop me from pushing them down”
“Please turn your head to the right and stop me pushing it back again”. Feel the left sternocleidomastoid at the same time. Repeat on other side.
Supplies intrinsic muscles of tongue. Ask patient to open mouth and observe for tongue fasciculations and wasting. Then ask patient to stick tongue out and move it from side to side. Tongue deviates to side of lesion.
“I have now completed my examination. I would also like to carry out a full neurological examination.”
Then summarise your findings eg Mr Jones is a 79 year old gentleman who is wheelchair bound but looks comfortable at rest. He does not report any olfactory deficit. Visual acuity was 6/6 in the right eye and 6/9 in the left. Pupils were equal and reactive to light. The visual fields were normal. Fundoscopy was not carried out etc…