Cranial nerve examination

Question 1

How would you consent the patient?

Answer 1

I would like to examine the nerves around your face and head, would that be Ok with you?

Question 2

What are you looking for on general inspection?

Answer 2

Visible discomfort 
Muscle wasting 
Facial asymmetry/ loss of facial expression
Ptosis/strabismus
Salivation

Question 3

How do you test CN1 (olfactory)?

Answer 3

Have you noticed any recent changes in your sense of smell?

Causes of anosmia:

Mucous blockage of the nose: preventing odours from reaching the olfactory nerve receptors.
Head trauma: shearing of the olfactory nerve fibres
Genetics: congenital anosmia.
Parkinson’s disease: anosmia is an early feature of Parkinson’s disease.
COVID-19

Question 4

How do you test CN2 (optic)?

Answer 4

Assess pupil size, shape and symmetry

Visual acuity- ask to read lowest line they can on Snellen chart with each eye covered ( wearing glasses if present)

Visual fields- ask patient to cover one eye and mirror them, then move finger in different areas and compare their visual fields to your own - ( tell them to say “yes” when they see it move)

Pupillary response- Accommodation:
1. Ask the patient to focus on a distant object (clock on the wall/light switch).

2. Place your finger approximately 20-30cm in front of their eyes (alternatively, use the patient’s own thumb).
3. Ask the patient to switch from looking at the distant object to the nearby finger/thumb.
4. Observe the pupils, you should see constriction and convergence bilaterally.

Direct light reflex - shine pen torch into eye and look for constriction of ipsilateral pupil
Consensual light reflex- shine pen torch and look for constriction of contralateral pupil

I would also carry out a fundoscopy

Question 5

How would you test CN3 (oculomotor), CN4 (trochlear) and CN6 (abducens) ?

Answer 5

First assess resting gaze and looking for ptosis (Oculomotor nerve pathology, Horner’s syndrome,
Neuromuscular pathology (e.g. myasthenia gravis)

Eye movements- “ I would like to assess the movements of you eyes now- please follow my finger with your eyes whilst keeping your head still and let me know if you experience double vision at any point”

• move finger in a H shape and state that you are looking for any difficulties with eye movements and nystagmus

Question 6

How do you test CN5 (Trigeminal)?

Answer 6

Test sensation on face bilaterally - ask patients to close eyes and ask if it feels the same on both sides- opthalmic, maxillary, and mandibular divisions

” I would like to test the sensation on you face if that is OK - I would like you to close your eyes and I’m going to touch you gently with this piece of cotton wool- please say yes if you feel it touching you and let me know if it feels different on one side than the other”

State would carry out corneal reflex if indicated

Ask to clench teeth and palpate temporalis and massester muscle

Ask to open jaw and move side to side to assess pterygoid function

Question 7

How do you test CN7 (Facial)?

Answer 7

“I’m going to ask you to do some facial expressions for me now if thats OK”

Raised eyebrows: assesses frontalis – “Raise your eyebrows as if you’re surprised.”
Closed eyes: assesses orbicular oculi – “Scrunch up your eyes and don’t let me open them.”
Blown out cheeks: assesses buccinator – “Blow out your cheeks and don’t let me deflate them.”
Smiling: assesses levator anguli oris and zygomaticus major – “Can you do a big smile for me?”

Question 8

How do you test CN8 (Vestibulocochlear)?

Answer 8

Ask if any recent changes in hearing

Ask pt to cover one ear and whisper a number in the other - repeat on both sides

Webers test- tuning fork on middle of forehead, ask if louder on one side or other
Rinne’s- place on mastoid process, ask to say when sound disappears , should still hear when fork placed in front of ear (Rinne’s positive = healthy)

Question 9

How do you test CN9 (Glossopharyngeal) and CN10 (Vagus)?

Answer 9

Ask pt to cough
Ask patient to open mouth and say ‘ahhh’ - assess for uvular deviation

Question 10

How do you test CN11 ( Accessory) ?

Answer 10

Ask to shrug shoulders and keep them up against resistance ( don’t let me push them down)

Ask to turn head against hand

Question 11

How do you test CN12 (Hypoglossal)?

Answer 11

look for wasting/fasciculation of tongue muscle
Protrude tongue and move to one side

Question 12

Next steps?

Answer 12

Further steps in completing your cranial nerve assessment would include:

taking a full history: if this hasn’t already been done.

additional examinations: you should offer to examine the peripheral nervous system of the upper and lower limbs
basic observations: (temperature, pulse, BP) if not already done

investigations such as imaging (CT/MRI) of the head if symptoms or signs indicated.