5. Cranial nerves

Question 1

intro to cranial nerve exam

Answer 1

“today I’ve been asked to examine you to see how well your your cranial nerves are working- these are the nerves that supply your nose, eyes, face, ears, mouth and neck”

“so this will involve me checking things like your vision, eye movements, facial movements and your hearing…”

“does that sound okay?”

“are you in any pain at all?”

Question 2

general inspection CN exam

Answer 2

Scars, neurofibromas, facial asymmetry, ptosis, proptosis, skew deviation of the eyes or inequality of the pupils.

Question 3

smell CN exam

Answer 3

Cranial nerve I - Olfactory - “any recent change to sense of smell?”, if needed do smell tests in each nostril, other one occluded

Question 4

Eyes CN exam

Answer 4

Vision - Cranial nerve II - Optic - “any changes to vision? Do you wear glasses or contact lenses?”
Visual acuity (>2 fingers, EO)
confrontation (visual fields) (2 fingers, EO),
attention (2 fingers),
accommodation (1 finger),
direct and consensual light reflexes (no fingers)

Movement - Cranial nerves III, IV, VI - SO4LR63 - H shape, I shape, “double vision?” “Pain on moving your eyes?” look for nystagmus

Question 5

to complete eye CN exam

Answer 5

“I would also like to do ophthalmoscopy and check colour vision”

Question 6

Face CN exam

Answer 6

Cranial nerve V - Trigeminal Sensation in three regions, motor : clench jaw whilst palpating temples and mandible, open jaw against resistance

Cranial nerve VII - Facial facial expressions: raise eyebrows, close eyes, close eyes against resistance, puff cheeks, purse lips, show teeth

Question 7

which muscle does occulomotor nerve supply

Answer 7

everything except superior oblique and lateral rectus therefore:

Levator palpebrae superioris - raises the upper eyelid.
Superior rectus muscle - rotates the eyeball backward, “looking up”
Medial rectus muscle - adducts the eye, “looking towards your nose”
Inferior rectus muscle - rotates the eyeball forwards, “looking down”

Question 8

which muscle does abducens nerve supply

Answer 8

lateral rectus
LR6

Question 9

which muscles does the trochlear nerve supply

Answer 9

superior oblique
SO4

Question 10

which eye muscles do each of the nerves supply

Answer 10

SO4LR63

SO4 - superior oblique 4th CN so trochlear
LR6 - lateral rectus 6th cranial nerve so abducens
3 - everyrthing else - 3rd CN - occulomotor

Question 11

ears CN exam

Answer 11

Cranial nerve VIII - Vestibulocochlear - cover opposite ear whisper a number at 15cm and 60cm. If abnormality → rinnes and webers

Question 12

mouth CN exam

Answer 12

Cranial nerve IX and X -Glossopharyngeal and vagus: change to voice? issues swallowing? note hoarseness, open mouth and say “ahh” - look at uvula. swallow a sip of water

Cranial nerve XII - Hypoglossal: observe tongue, protrusion of tounge, tongue to cheek against resistance

Question 13

shoulders CN exam

Answer 13

Cranial nerve XI - accessory shrug shoulders against resistance, turn head against resistance

Question 14

tounge hypoglossal

Answer 14

intrinsic muscles - shape and size for example, in tongue rolling – and have a role in facilitating speech, eating and swallowing.

extrinsic muscles except palatoglossus (innervated by vagus)

Question 15

vagus tounge

Answer 15

palatoglossus muscle (an extrinsic muscle)

elevation of the posterior tounge

Question 16

anterior 2/3 sensation and taste tounge

Answer 16

sensation: trigeminal nerve (CNV)

taste: facial nerve

Question 17

posterior 1/3 of tounge sensation and taste

Answer 17

both glossopharyngeal nerve CNIX

Question 18

tounge innervation

Answer 18

motor
- hypoglossal except for posterior tounge vagus (palatoglossus muscle)

sensation
- ant 2/3 trigeminal
- post 1/3 glossopharyngeal

taste
- ant 2/3 facial
- post 1/3 glossophayrngeal

Question 19

how to test hypoglossal nerve

Answer 19

Ask the patient to open their mouth and inspect the tongue for any wasting or fasciculation
Ask the patient to protrude the tongue and move from side to side
tounge against cheek against resistance

Question 20

innervation of gag reflex

Answer 20

The afferent limb of the gag reflex is the glossopharyngeal nerve, and the efferent limb is the vagus nerve.

Question 21

examination of glossophayrngeal and vagus

Answer 21

open mouth and say “ahh” - look at uvula
swallow a sip of water

change to voice? issues swallowing?

Question 22

uvula deviation?

Answer 22

uvula deviates away from site of lesion in X

Question 23

presentation vagus nerve pasly

Answer 23

ipsilateral paralysis of the soft palate, pharynx, and larynx. The voice is hoarse or nasal, the involved palatal arch is paralyzed, and liquids will enter the nasopharynx or trachea. The vocal cord on the involved side is paralyzed.

refractory tachycardia

Question 25

examination vision loss

Answer 25

Inspection: is it RED (acute angle closure)

Optic nerve: acuity, visual fields, attention, accommodation, pupils, colour vision
- Pupil unreactive/not responding/ well to light/RAPD suggests optic nerve dysfunction therefore could be due to anterior optic neuropathy (GCA or TIA), optic neuritis etc

Eye movements: H test, any double vision? any pain on movement? (any CN palsys?)

To complete…
Opthalmoscopy
HbA1c, BP
Referral for slit lamp examination

Question 26

what should you be able to label on fundoscopy

Answer 26

optic disc
optic cup

macula
fovea

retinal vein
retinal artery

Question 27

features of third nerve palsy

Answer 27

eye is deviated ‘down and out’
ptosis

if surgical:
pupil may be dilated (sometimes called a ‘surgical’ third nerve palsy)
painful

Question 28

causes of third nerve palsy

Answer 28

consider surgical :
eg posterior communicating artery aneurysm

other serious:
- false localizing sign* due to uncal herniation through tentorium if raised ICP
- Weber’s syndrome stroke

other:
diabetes mellitus
vasculitis e.g. temporal arteritis, SLE

Question 29

features of fourth nereve palsy

Answer 29

Trochlear nerve
LR6SO4

Defective downward gaze –> vertical diplopia
Nasal upshoot is how it looks!!!!
head tilted to the other side

Question 30

causes of 4th nerve palsy

Answer 30

• CONGENITAL (esp if head tilted)
  Vasculopathy (htn, diabetes)
  Tumour
  Congenital (esp if head tilt)
  Trauma

Question 31

features of 6th nerve palsy

Answer 31

defective lateral gaze

appear cross-eyed

Question 32

causes of 6th nerve palsy

Answer 32

think RAISED ICP eg IIH

Vasculopathic
Tumour

Question 33

differentials for diplopia

Answer 33

eye muscle problem:
- myasthenia gravis
- graves
- strabismus

neurological:
- head injury
- stroke
- migraine
- tumour
- wernikes

Nerve problem (eg 3rd CN, 4th CN or 6th CN)
- diabetes
- congenital
- raised ICP
- MS
- guilian barre

Question 34

examination ?diplopia ?strabismus

Answer 34

Cover/uncover : shows manifest strabismus (when other eye is covered, the squint corrects itself)

Alternate cover test : shows latent strabismus (squint present when covers so when uncovered it moves in opposite direction)

Fundoscopy (or red reflex) to rule out retinoblastoma, cataracts and other retinal pathology

Visual acuity

Question 35

how to interpret snellen chart?

Answer 35

6/6 is normal eg 20/20 in america
1st number is what pt can see
2nd number is average number

6 metres from snellen chart

therefore
9/6 is rly good
2/6 is bad

Question 36

how to use a snellen chart

Answer 36

pt stood at 6 metres the whole time. cover one eye and test separetly

interpret it off the chart

which metre they land on is first number