Cranial Nerves Examination and common pathologies Agata Plonczak Tuesday Jan 15 th 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: • C ount F ingers held in front of their face • See H and M ovements • P erceive L ight • 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 ��������������
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, Lateral medullary fractures 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?
Recommend
More recommend
