cranial nerve examination final - medical student · pdf filetrochlear nerve palsy: rare in...
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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?