Cranial nerve examination

Question 1

CN1

Answer 1

Olfactory- smell (sensory)

Test:
– smell test, unilateral smell test

Outcomes:
– Anosmia (partial or full loss of smell)- genetics, parkinsons, fracture of cribriform plate
– parosmia (distorted sense of smell)- bacterial or viral infections
– hyperosmia (oversensitivity to smell)- migraine, genetics, epilepsy

If a patient doesn’t notice that their sense of smell has gone, then they might notice that their sense of taste has gone

Question 2

CN2

Answer 2

Optic- sight (sensory)

Test:
– first analyse eyes yourself, looking at position of the eyelids
– can look for proptosis (bulging of the eyes) from above the head

• can do the snellen wall chart
• nasal and temporal fields of vision
• pupillary reflex (can perform to check oculomotor and optic at the same time)

Question 3

Optic chiasm

Answer 3

Part of the brain where the optic nerves cross and is a primary importance to the visual pathway

Location:
– at base of the brain inferior to the hypothalamus
– approx 10mm superior to the pituitary gland within the suprasellar cistern

It contains one- hand of each nerve’s axons

Optic gliomas:
– they are rare
– optic gliomas (tumours) can grow within the chiasm or in conjunction with hypothalamic tumours. They can directly affect the optic nerve

Symptoms:
– bulging eyes or vision loss
– squinting or involuntary eye movement
– elevated intracranial pressure
– loss of appetite and fat reduction

Edinger-Westphal nucleus:
– a small parasympathietic motor nucleus in the midbrain and one of the 2 nucleus’ for the oculomotor nerve
—- function- receives input from the locus coeruleus in response to the light hitting the retina, which then prompts the nucleus to send a forward signal that synapses at the postganglionic cells of the ciliary region

Question 4

CN3, CN4 and CN6

Answer 4

CN3, 4 and 6 always tests together

CN3, 7, 9 and 10 are all parasympathetic

Eye movement

CN3- supplies 4 out of 6 eye muscles
CN4- supplies superior oblique (in and down)
CN6- supplies lateral rectus (outwards)

Test:
– H test- get pt to focus on an item (pen) and move it in a H motion

– light pupillary reflex as CN3 is parasympathetic
—- if pupils dont restrict, this may be because of damage to the optic nerve as optic nerve is responsible for moving information into the eye and oculomotor out of the eye (Edinger-Westphal nucleus as well)

Outcomes:
– ptosis (where upper eyelid droops over eye)- innervation to the levator palpebrae superioris

Divergen squint

Pupil dilation

Eye movements restricted

Trochlear:
– vertical diploma (double vision when looking down)

Abducens:
– medial gaze- lateral rectus fails, meaning medial rectus will pull the eye inwards

May also have an inability to look lateral during the H test

Question 5

CN5

Answer 5

Trigeminal nerve (both)- face and cheek sensations and jaw movement
– opthalmic and maxillary (sensory)
– mandibular (motor to the muscles of mastication)

Test:
– sharp and soft sensory test

– mastication test:
—- get pt to chew and analyse
—- feel muscles of mastication (masseter, temporalis and lateral pterygoids)

– jaw reflex
– corneal reflex

Outcomes:
– loss of sensation in face (Bell’s palsy, trigeminal nerve palsy)
– loss of distinction between sharp and soft
– weakness or inability to masticate
– increased reflex (mouth closing)
– loss of blinking reflex

Question 6

CN7

Answer 6

Facial nerve (both)- taste and facial expression (parasympathetic)

Test:
– ask pt about their test, hearing and saliva in their mouth and tears
– pt with facial nerve palsy, may have a dry mouth and have the inability to cry

– facial expression test:
– ask pt to pull, surprised, angry and a smiling face
– get pt to blow out cheeks and resist your pressure inwards
– get pt to close their eyes and resist you opening them

Outcomes:
– hypogeusia (reduced taste ability)
– agues (loss of taste completely)

– loss of hearing noted (can test in conjunction with CN8)

– Ramsey Huny syndrome (herpes zoster oticus)- occurs when a shingles outbreak affects the facial nerve near one of your ears.
—- can cause facial paralysis and hearing loss in the affected ear

– facial palsy (Bell’s palsy or stroke)

Question 7

CN8

Answer 7

Vestibulocochlear/auditory (sensory)- hearing and balance

Test:
– ask the pt about their hearing in general

– Weber’s test- place a 512Hz tuning fork onto the pt forehead (bone conduction), pt should be able to hear it in both ears

– Rinne’s test- 512Hz tuning fork over mastoid process (bone conduction), when pt can no longer hear place it in the air next to ear (air conduction)

– numbers repetition test

Outcomes:
– numbers test- loss of air conduction
– Weber’s- may hear noise in only one ear, then it might be conductive deafness

– Rinne’s- bone conduction or air conduction loss

Question 8

CN9/10

Answer 8

Glossopharyngeal and Vagus (parasympathetic)

Test:
– ask pt to cough
—- assess the strength of the cough
– voice may be hoarse
—- see if there’s an dysarthria (associated with bilateral CN10 palsies)
– ask the pt’s about any dizziness or syncope
—– as vagus may play a role in hypotension

– swallowing test- look in the pt mouth when they are swallowing, look at the deviation of the ulna
—- pt should be in a semi-recumbent position
—- the usual should devote upwards if its normal when swallowing, if it deviates downwards then it’s a sign
—- can also get pt to say ‘Ah’

– gag reflex test

– blood pressure- check as vagus can cause hypotension

Outcomes:
– uvula deviation away from the palsied side
– weakness in the patients voice
– loss of gag reflex
– hypotension
– dysphagia (trouble swallowing)
—- associated with bilateral CN10 lesions

Question 9

CN11

Answer 9

Accessory- (motor)- neck and shoulder movement (pharynx, trapezius and SCM)

Test:
– SCM test:
—- rotate pt head and pt tried to rotate against your contact

– trapezius test:
—- pt shrugs shoulders up, resist your pressure of pushing down

Trembling is fine for both its the muscles not firing is what you need to worry about

Outcomes:
– weakness
– muscle wasting

Question 10

CN12

Answer 10

Hypoglossal (motor)- tongue movement and throat muscles movement

Test:
– Resist tongue movement-
—- get pt to stick their tongue into their cheeks, one cheek at a time, press into the tongue and they have to resist

– tongue protrusion:
—- get pt to stick their tongue out, their tongue will move towards the palsy lesion
– due to the overaction of the strong genioglossus muscles

can be damaged nuclear, supranuclear and infra nuclear

Outcomes:
– tongue deviation
– tongue weakness

Question 11

Muscles of facial expression CN7 - E

Answer 11

Orbital
- orbicularis oculi
- corrugator supercili

Nasal
- nasalis
- procerus
- depressor septi Nasi

Oral
- orbicularis oris
- buccinator
- minor oral muscles
- lower
- upper

Question 12

Muscles of mastication CN5 - E

Answer 12

(Temporomandibular joint)

Masseter
Temporalis
Medial pterygoid
Lateral pterygoid