Examination of the Cranial Nerves

transcript

EXAMINATION OF THE CRANIAL NERVES

Anwar Wardy W

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Cranial Nerves: Motor and Sensory Functions

Figure 28.4 Dorsal aspect of brain with cranial nerves noted.

Components of the Neurological Examination(Cranial Nerves)

Olfactory Nerve (I)

perception (recognition, hallucinations)

Optic Nerve (II)visual acuity (unaccommodated / accommodated)visual fieldscolor visionpupilsvisual reflexes

light reflexes (direct / indirect)accommodation reflex

funduscopic exam

Components of the Neurological Examination(Cranial Nerves)

Ocular Motor Nerves (III,IV,VI) inspection

palpebral fissures (ptosis, proptosis)

ocular position (strabismus, gaze shifts)

head position (compensation)

spontaneous movements (nystagmus)

common complaints

diplopia

blurred vision

ocular movements (monocular and binocular)

tracking (pursuit)

volitional

ocular motor testing

cover testing (heterotropia/heterophoria)

red glass test

corneal light reflection test

Components of the Neurological ExaminationCranial Nerves

Trigeminal Nerve (V)sensory (ophthalmic, maxillary, mandibular)

threshold and symmetry to tactile (and thermal) stimuli(corneal reflex)

motormasseter and temporalis strength

reflexjaw jerk

Facial Nerve (VI)inspection

forehead, palpebral fissures, nasolabial fold, corner of mouthmotor

upper face (frontalis, orbicularis oculi)lower face (zygomaticus, orbicularis oris)

enunciationlabial sounds – “M”

(autonomic)(lacrimation)

(sensory)(taste – anterior 2/3 of tongue)

Components of the Neurological Examination Cranial NervesVestibulocochlear Nerve (VIII)

cochlear divisionscreening test

finger rub (auditory threshold)deficit characterization (sensorineural vs. conduction)

WeberRinne

vestibular divisioninspection

nystagmustests of function

past pointingmarching in placevestibulo-ocular reflexes

oculocephalic reflex (doll’s head maneuver)head thrust and head shake tests

oculovestibular reflex (caloric testing)walking (oscillopsia)

provocative testsDix-Hallpike maneuver (Nylen-Barany )

Components of the Neurological ExaminationCranial Nerves

Glossopharyngeal (IX) and Vagus (X) Nerves

inspection

position of uvula and soft palate at rest

movement of uvula and soft palate with “AAHH”

(glottis - position of the vocal folds)

auscultation

hoarseness

stridor

enunciation

pharyngeal sounds – “K”

(pharyngeal ((gag)) reflex)

(observe swallowing)

Components of the Neurological Examination Cranial Nerves

Spinal Accessory Nerve (XI)inspection

atrophy, head tiltstrength testing

(upper) trapezius – shoulder shrugsternocleidomastoid – head turning

Hypoglossal Nerve (XII)inspection (tongue in floor of mouth)

atrophy/furrowingfasciculations

inspection (on protrusion)midline/deviation

enunciationlingual sounds - “L”

OLFACTORY NERVE (I)

• Test with alcowipes, coffee etc.

• Unilateral anosmia may be significant

• Bilateral anosmia: commonest cause viral

• Classical pathology:olfactory groove meningioma

• Basal skull fractures another potential cause (unilateral or bilateral)

OPTIC NERVE (II)

• Visual acuity

• Visual fields to confrontation

• Pupillary reflexes (II and III)

• Fundoscopy (papilloedema, optic atrophy, retinitis pigmentosa)

VISUAL ACUITY

• CORRECTED (ie brain not lens)• Each eye separately• Snellen charts for distance and near vision

reading charts for near vision• Best approximation: small print (or

equivalent) at normal reading distance • If unable, finger counting, hand

movements, perception of light

VISUAL FIELDS

• Often forgotten but very important• First do a bilateral screening test: will

uncover the majority of significant visual field defects immediately

• Go on to check each eye separately, ask about scotomata

• Mention checking for blind spot enlargement

COMMON FIELD DEFECTS

• HOMONOMOUS HEMIANOPIA: lesion posterior to the optic chiasm (eg posterior cerebral artery territory infarction)

• BITEMPORAL HEMIANOPIA: lesion at the optic chiasm (eg pituitary tumour)

• BLINDNESS ONE EYE: lesion in eye, retina or optic nerve

PUPILLARY RESPONSES

• Light reflex is the clinically significant one

• Afferent limb = II, efferent limb = III

• Look at pupillary sizes

• Direct and consensual response

• Look for afferent pupillary defect (optic nerve lesion)

PUPILLARY ABNORMALITIES

• One large pupil: IIIrd nerve palsy, iris problem (eg traumatic midriasis), unilateral dilator eye drops

• Small pupil: Horner’s syndrome, Argyll-Roberston pupil (small, irregular, reacts to accommodation but not to light)

• Bilateral small pupils: drugs (opiates), pontine lesion (haemorrhage)

HORNER’S SYNDROME

• Oculosympathetic paralysis

• A good lateralising sign but a poor localising sign

• Ptosis, miosis and sometimes unilateral anhydrosis of face

• Look especially at neck, supraclavicular fossa and hand (Pancoast’s tumour)

Eye movements (III, IV and VI)

• IV: TROCHLEAR NERVE (supplies superior oblique muscle)

• VI: ABDUCENT NERVE (supplies lateral rectus muscle)

• III: OCULOMOTOR NERVE: all other extraocular muscles, also carries parasympathetic (constrictor) fibres to pupil, and fibres to levator palpebrae superioris

EYE MOVEMENTS

• Look at eyes in primary position of gaze

• IIIrd nerve palsy: eye often ‘down and out’

• VI nerve palsy: often eyes convergent (unopposed medial rectus)

• Look at pupils

• Look for ptosis

EYE MOVEMENTS

• Follow a moving object (finger, end of tendon hammer) and ask for any symptomatic diplopia

• Determine position/s causing maximum diplopia

• Ask about separation of images (horizontal or oblique)

• Check diplopia is BINOCULAR

TYPICAL EXAM CASES

• IIIrd nerve palsy: ptosis, eye ‘down and out’, diplopia in all except one direction of gaze, may have dilated pupil ( a ‘surgical’ IIIrd nerve palsy

• VI nerve palsy: eye convergent, diplopia on lateral gaze only, horizontally separated images

CAUSES OF COMPLEX OPTHALMOPLEGIA

• Dysthyroid eye disease

• Myasthenia gravis (look for fatiguability of diplopia and ptosis)

• Mitochondrial disorders

INTERNUCLEAR OPHTHALMOPLEGIA

• Nystagmus in the abducting eye• Failure of adduction of the other eye• Both eyes move normally when tested

individually• Lesion in the MEDIAL LONGITUDINAL

FASICULUS (on the side WITHOUT nystagmus

• Can be bilateral

TRIGEMINAL NERVE (V)

• Most important function is sensory• Ophthalmic, maxillary and mandibular divisions• Test with light touch and pinprick in all 3

divisions, comparing each side• Corneal reflexes (afferent limb V, efferent limb

VII)• Know something about trigeminal neuralgia

(examination is normal in these cases)

FACIAL NERVE (VII)

• Supplies the muscles of the face

• DIFFERENTIATE AN UPPER MOTOR NEURON FROM A LOWER MOTOR NEURON LESION

• Upper motor neuron lesion: milder, spares the forehead, no Bell’s phenomenon

VESTIBULOCOCHLEAR NERVE (VIII)

• For clinical examination purposes, forget the vestibular element

• Check hearing approximately in each ear

• If reduced, determine whether conductive (BC >AC) or sensorineural (AC>BC) deafness

GLOSSOPHARYNGEAL (IX) AND VAGUS (X)

• Tested together• Speech, palate, cough, swallow, (gag reflex)• Bulbar palsy: bilateral LMN lesions of IX

and X: poor palatal movement, nasal speech, nasal regurgitation of fluids

• Pseudobulbar palsy: bilateral UMN lesions: ‘hot potato’ speech, no nasal regurgitation, additional frontal lobe signs

ACCESSORY NERVE (XI)

• Cranial and spinal roots

• Cranial roots: sternocleidomastoid (note direction of head turn)

• Spinal roots: trapezius (shoulder shrug)

HYPOGLOSSAL NERVE

• Movement of the tongue

• Look for wasting and fasiculation of the tongue

• Deviation of tongue on protrusion

• Tongue movements including power

Examination of the Cranial Nerves

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