Cranial NervesExamination and common pathologies

Agata PlonczakTuesday Jan 15th 2013

Approach to Examination

Where is the lesion?

Cranial nerves can be affected as single nerves or in

groups

There are 12 cranial nerves arising from the

brainstem

The olfactory (I) nerve

• Sensory nerve conveying the sense of smell

Brainstem –anterior view

The olfactory (I) nerve -examination

• Rarely performed

• Ask patient if they noticed any change of smell

1.Check nasal passages clear

2.Ask pt to close eyes and shut one nostril with one

finger

3.Use common, easily recognizable, non-irritant

substance eg orange, coffee

CN I –abnormal findings

Anosmia usually due to nasal rather than neurological

disease

Olfactory nerve is vulnerable as it passes through

cribriform plate

May occur in Parkinson’s or Huntington’s diease

The optic (II) nerve

• Sensory nerve conveying the sense of vision from

the retina

The optic (II) nerve -anatomy

The optic (II) nerve -examination

1. Visual acuity

2. Visual fields including sensory inattention

3. Colour vision

4. Pupillary responses

5. Fundoscopy

Visual acuity

• Sharpness, clarity of vision

• Assessed formally using a Snellen chart

• In good light patient should stand 6m away from

chart

• Number above each line =distance from which a

person with normal sight should be able to read

from

• Indicate results as: distance from chart/distance it

should be read eg. 6/24 (normal vision = 6/6)

Visual acuity cont.

• If the patient can’t read any letters, record if they

can:

• Count Fingers held in front of their face

• See Hand Movements

• Perceive Light

• Record as: CF, HM, PL or NPL

Visual fields

• Normal visual field extends 160 degrees horizontally

and 130 degrees vertically

• Blind spot is located 15 degrees to the temporal side

of the visual fixation

• Test by confrontation

• Sit 1 metre apart at the same level, ask patient to

keep looking into your eyes

• Start with sensory inattention

Visual field defects

Pupillary responses

• Autonomic nervous system and integrity of iris

determine the size of resting pupil

• Parasympathetic fibres

� pupillary constriction

• Sympathetic fibres

� pupillary dilatation

Pupillary responses –examination

• Examine for shape and symmetry in good light

• Ask patient to fix the eyes on a distant point ahead

• Bring a bright light from the side to shine on the

pupil

• Look for direct and consensual light reflex (+/-

RAPD)

• Test accomodation

The oculomotor (III), trochlear (IV)

and abducens (VI) cranial nerves

• CN III supplies the levator palpebrae superioris which opens the upper eyelid as well as all extraocular muscles but SOL

and LR

• In addition it carries parasympathetic fibres causing

constriction of the pupil

• CN IV � superior oblique

• CN VI � lateral rectus

Brainstem –anterior view

CN III, IV and VI –examination

• Inspect the position of eyelids

• Ask the patient to follow your index finger in vertical,

horizontal and oblique planes avoiding extremes of

gaze, drawing an imaginary H line in front of them

• Ask for any diplopia

• Examine for saccadic eye movements

CN III, IV, VI –abnormal findings

?

Horner’s syndorme

Interuption of sympathetic nerve suppy to the iris

1.Miosis

2.Enopthalmos (sunken eyes)

3.Ptosis

4.Ipsilateral anhidrosis

Causes: demyelination, vascular disease, Pancoast

tumour , syringomyelia, carotid aneurysm

?

Complete ptosis associated with widely dilated pupil, eye paralysed with outward and downward deviation

Causes: mononeuritis multiplex, posterior communicating

artery aneurysm, midbrain lesion

CN IV and VI palsies

Trochlear nerve palsy: rare in isolation, diplopia on

looking down and in often noticed on walking down

stairs, compensated for by turning of head

Abducens nerve palsy: loss of eye abduction, horizontal

diplopia on looking out, often false localising sign!!!

Nystagmus

• Involuntary, often jerky eye oscillations

• ≤ 2 beats and at extremes of gaze normal

Horizontal:

Often due to vestibular or cerebellar lesions

If more in whichever eye abducting can be due to MS: -INO

If associated with deafness, tinnitus: Meniere’s

If varies with head position: consider BPPV

Vertical:

ask neurologist

CN IV and VI palsies

Trochlear nerve palsy: rare in isolation, diplopia on looking

down and is often noticed on walking down stairs,

compensated for by turning of head

Abducens nerve palsy: loss of eye abduction, horizontal

diplopia on looking out, often false localising sign!!!

Trigeminal (V) nerve

• Sensory: somatic sensation to face

• Motor: muscles of mastication (masseters, temporalis,

pterygoids)

• Corneal reflex

• Jaw jerk

V1: opthalmicV2: maxillaryV3: mandibular

Brainstem –anterior view

Trigeminal (V) nerve -examination

• Sensory: assess light touch for each branch, choose 3 spots on each side (ie forehead, cheek and mid-way along jaw) + test pin-prick sensation

• Motor: ask patient to clench their teeth and feel for muscle bulk

• Corneal reflex: look for direct and consensual blinking

• Jaw jerk: normal response: absent or just present

?

Trigeminal (V) nerve –abnormal findings

• Sensory lesions are much more common than

motor

• Absent corneal reflex may be the first sign of

opthalmic Herpes

• Brisk jaw jerk occurs with bilateral upper motor

neurone lesions above the pons

Facial (VII) nerve

Facial (VII) nerve -examination

• Ask patient to raise their eyebrows

• Ask the patient to show their teeth

• Next close eyes against resistance

• Then blow out cheeks

• Taste can be tested with sweet/salt solutions, rarely

done

?

Facial (VII) nerve

• As forehead has bilateral innervation in the brain,

only lower 2/3 is affected in UMN lesions but ALL

side of the face in LMN lesions.

• LMS: Bell’s palsy, polio, otitis media, skull fracture,

acoustic neuroma, Herpes Zoster

• UMN: tumour, stroke

Vestibulocochlear (VIII) nerve

• Auditory –sense of hearing

• Labirynthine –sense of balance

Vestibulocochlear (VIII) nerve -examination

1. Simple test of hearing• Whisper a number into patient’s ear and ask to repeat, repeat with other ear

2. Rinne’s test • tap a 512Hz tuning fork.

Compare subjective loudness when

held close to external auditory meatus

vs when base applied to mastoid

3. Weber’s test: • tap a 512 tuning fork

hold against vertex of forehead at midline

Assessment of tuning fork tests

Condition Rinne’s Weber’s

Normal hearing positive Heard in midline

Conductive deficit negative Heard louder on affected

side

Sensory deficit positive Heard louder on non-

affected side

Glosopharyngeal (IX) and vagus (X) nerves

Glosopharyngeal: •Sensation to posterior 1/3 of the tongue

•Motor to stylopharyngeus

•Autonomic to the parotid gland

Vagus: •Autonomic: parasympathetic innervation to heart, lungs, foregut

•Motor to larynx, soft palate, pharynx

•Sensory to dura matter of posterior cranial fossa, small parts of external ear

Brainstem –anterior view

CN IX and X -examination

1. Soft palate: observe uvula; will deviate away from

lesion (CN X)

2. Speech: listen for dysphonia

3. Cough

4. Test swallow –terminate if any signs of aspirating

5. Gag reflex: produces elevation of the palate.

!unpleasant, don’t test unless you suspect a CN IX

or X lesion.

Common causes of CN IX and X lesions

Unilateral of IX and X

Skull base tumours,

fractures

Lateral medullary

syndrome

Recurrent laryngeal

Lung cancer Thyroid surgery

Bilateral X

Progressive bulbar palsy Psedudobulbar palsy

(CVA, MS)

Accessory (XI) nerve

Motor to the trapezius and sternocledomastoid

muscles

Note that each cerebral hemisphere controls the

ipsilateral sternocleidomastoid and contralateral

trapezius

Brainstem –anterior view

Accessory (XI) nerve -examination

Inspection: face the patient to inspect for wasting or

hypertrophy; stand behind the patient to inspect for

wasting or assymetry of trapezius

Testing power:

Accessory (XI) nerve –abnormal findings

Surgery in the posterior triangle of the neck

Local invasion by tumour

Wasting and weakness of trapezius characteristic of

dystrophia myotonica

Head drop may be seen in myasthenia and motor

neurone disease

Hypoglossal (XII) nerve

Innervates the muscles of the tongue

Inspect the tongue for wasting and fasciculations

Ask the patient to protrude the tongue.

If there is a unilateral lesion the

tongue will deviate towards the side of the lesion

Brainstem –anterior view

Thank you

Any questions?