Cranial nerve examination

Cranial nerve examination

Cranial nervesI. OlfactoryII. OpticIII. OcculomotorIV. TrochlearV. TrigeminalVI. AbducentVII. FacialVIII. AuditoryIX. GlossopharyngealX. VagusXI. Spinal accessoryXII. Hypoglosseal

Summary of Function of Cranial Nerves

FUNCTIONAL TYPES

Pure sensory Olfactory Optic Auditory

Pure motor Trochlear Abducent Accessory Hypoglosseal

Mixed nerves Trigeminal Facial Glossopharyngeal Vagus Occulomotor

Cranial Nerve I: Olfactory

Function

Carries the sensation of smell from nasal mucosa to olfactory bulb

Purpose of the testTo determine any impairment of smell is

unilateral or bilateralWhether impairment is due to any local nasal

disease or neural lesion

Method of testingSmall bottles containing

essences of very familiar odour are required

•Coffee

•Lemon

•Chocolate

•Asafetida etc

PROCEDURE

Compress 1 nostril & sniff the taste odour twice

Ask whether he can smell or identify odour

Repeat test on other nostril & ask if smellis similar in both nostril

Allow odour to disperse & repeat test with other2 test odour, ask he can distinguish smell

Interpretation of result Who can recognize & name odours quickly (females) Who can recognize but difficult in naming (males) Who can smell & know difference but neither recognize

nor naming • The above 3 should be accepted as normal

Who feel each odour is similar but is distorted & unpleasant (parosmia)

Those who cant smell anything or is much reduced compared to the other (anosmia)

Those whose responses are vague & variable

Common causes of anosmia Acute/chronic inflammatory nasal disease Heavy smoking Head injury Intra cranial tumour compressing the

olfactory bulb Atrophy of olfactory bulb Chronic meningeal inflammation Parkinson’s disease

Cranial Nerve II: Optic

Function

Carries the visual impulses from the retina to the optic chiasma & in the optic tract to the lateral geniculate body

The impulse acts as an afferent pathway for the pupillary light reflex

Purpose of the testTo measure aquity of vision & determine if

any disease is due to local occular disease or neural impairment

To chart the visual field

Method of testingVisual acuity

• The standard snellen’s chart can be used for vision & the Jaegar type card can be used for near vision

[the commonest causes of

visual error lies in the eye only]

Visual fieldPurpose:

• To chart periphery of visual field

• To detect position, size & shape of the blind spot

Confrontation test

Instruct Pt to indicate appearance of the object

Pt covers left eye & examiner right

Pt & examiner sit face to face

PT moves the test object from outside the visual field towards midline

Common causes Total unilateral loss of vision: optic nerve

lesionHomonymous hemianopia: lesion between

optic tract to occipital cortexBitemporal hemianopia: lesion of optic

chiasma

Occulomotor, Trochlear, Abducent

Function Controls the external occular muscles &

elevators of the lidsAlso regulates the pupillary muscles

Purpose of the test Inspect pupils to rule out a local disease,

peripheral lesion or a nuclear involvementExamine eye movement & determine if

defects is muscular origin or neural involvement

To detect nystagmus

Method of testingObservation

• Presence & absence of ptosis & squint

• Whether unilateral or bilateral

• Constant or variable

• Size, shape, equality & regularity of the pupils

Reaction to light Reduce illumination of room & vision

should focus on a far objectA bright beam of light is shone from the side

of one eye Repeat on the other side

[the pupil should constrict briskly]Shield one eye & perform test on the other

& see for consensual reaction

Reaction to convergence & accommodation for near vision

Fix vision on a distant object & instruct to look in a near object

Place finger tip in front of the bridge of the nose (22 cm)

Then return to the far object Observe pupillary reaction in both

Examination of occular movement Observe lagging of one

or both eye• Observe nystagmus

Analysis of diplopiaShield one eye with a transparent red shieldObject is moved from left to right, up & downAsk if -

• He sees 1 or 2 object

• Object lies one above the other or side by side

Rules governing analysis of diplopiaSeparation of image is greatest in the

direction in which the weak muscle has its purest action

False image is displaced farthest in the direction in which the weak muscle should move the eye

Analyzing nystagmusWatch the patients eye while talking Ask to look at a definite point & move the

point from left to right & up to downHold each end position for 5 sec & assess

nystagmus (direction, rate amplitude)

Common causes of paralysis Pontine lesions Neoplasms Vascular accidents Demyelinating disease Meningeal inflammation Tumour of base of skull Increased intra cranial pressure Head injury[Total paralysis of III, IV & VI nerve indicates a lesion in

cavernous sinus (carotid aneurism)]

Cranial Nerve V: Trigeminal

Function Carries all forms of sensation from the face,

anterior scalp,eye & the anterior 3rd of the tongue

Also supplies the muscles of mastication

Purpose of the test To determine any sensory impairmentTo determine unilateral or bilateral motor

weakness & determine UMN from LMN

Method of examination Superficial sensory asst from mainly 6 areas

(mainly light touch & pain)

• Forehead & upper part of the side of nose (ophthalmic)

• Malar & upper lip region (maxillary)

• Chin & anterior part of tongue (mandibular)

Interpretation Total loss of sensation: lesion of ganglion or

sensory rootTotal sensory loss over 1 division: partial

lesion of ganglion or root Touch only lost: pontine lesion affecting

sensory nucleusPain & temp lost: dissociate anesthesia

(seringobulbia)

Corneal reflexUsing a cotton piece the

cornea is teasedNormal response is a

bilateral blink

(facial nerve forms the efferent loop of the reflex arc)

Interpretation No closure: ophthalmic division of the facial

nerveNo response in either lid when abn. is tested

& bilateral blink when normal is tested: V nerve lesion

No response of the affected side whichever side is tested: VII nerve lesion

Motor assessment Muscles of mastication Have Pt bite against resistance Have Pt protrude mandible

against resistance Have Pt go into lateral

excursive movts against resistance

Jaw jerk

Common causesTumours of base of skull Chronic meningeal lesion Trigeminal sensory neuropathyAcoustic neuromaSyringomyeliaMultiple sclerosis

Cranial Nerve VII: Facial

Function Supplies the muscles of facial expression

including platysma & stapedius muscle Secretomotor fibers to the lacrimal gland &

the salivary glandCarries sensation of taste from anterior 2/3

of tongue & general sensation from external acoustic meatus

Purpose of the testTo detect any unilateral or bilateral

weakness of facial muscles (UMN or LMN)Detect impairment of taste

Method of testing Observation

• Symmetry and asymmetry of face

• Nasolabial fold & wrinkle on forehead

Ask the Pt to close the eyes, raise the eyebrows, blow out the cheek, whistle etc

Examination of taste The four primary taste (sweet, salt, sour,

bitter) can be carried out by using sugar, salt, vinegar & quinine

The side of the tongue is moistened by the test substance

Ask the Pt to indicate taste by pointing

Secretomotor function The flow of tears of two side can be

compared by giving ammonia to inhale which will result in tearing of eye

The flow of saliva can be tasted by keeping a spicy substance in the tongue & the tip is raised to observe the sub maxillary salivary flow

Reflexes

Corneal reflex Nasopalpebral reflex: tap on the

nasopalpebral ridge will produce closure of both eyes. In bells palsy there is failure to close on the affected side

Common causes of facial paralysisNeoplasm affecting thalamus: unilateral

emotional paralysisParkinsonism : bilateral emotional paralysisCVA neoplasm, MND: bilateral UMN palsyBell’s palsyGBS

Cranial Nerve VIII: Vestibulocochlear

Function Carries the impulses of sound from the hair

cell of organ of corti to cochlear nucleus in pons

Control balance through vestibular nerve

Purpose of the testTo determine any deafness is bilateral or

unilateralWhether deafness is due disease of middle

ear or cochlear nerveTo determine the disturbance of vestibular

functions

Test of hearing Observe if the patient turns

one ear towards youEvaluate hearing using a

ticking watch, rub fingers together, whisper.

Rinne’s testStrike a tuning fork gently, hold it near one

external meatus & ask the Pt if he can hear itPlace it on the mastoid, ask if he can still

hear it & instruct him to say “NOW” when sound ceases, & keep it on the external meatus again (normally the note is still audible)

Interpretation In middle ear deafness – the note is not heardIn nerve deafness – air & bone conduction

are reduced but air remains better

Weber’s testThe fork is place on the vertexAsk the Pt if he can hear the sound all over

the head, in both ears or in one earIn nerve deafness the sound appear to be

heard on the normal earOn chronic middle ear disease it is conducted

to the abnormal ear

Common causes of deafnessDisease of external & middle ear &

Eustachian tubeProlonged exposure to loud noise Old ageMeningitis Demyelinating disease Deafness due to drugs

Test of vestibular functionObserve equilibrium as patient

walks or standsObserve abnormal eye movtsAsk for -

• Dizziness

• Falling

• Nausea and vomiting

Cranial Nerve IX: Glossopharyngeal

Function

General Sensory: posterior 1/3 of tongue, tonsil, skin of external ear, tympanic membrane & pharynx

Visceral Motor: parasympathetic stimulation of parotid gland, & controls blood

vessels in carotid body

Visceral Sensory: subconscious sensation

from carotid body & sinus

Special Sensory: carries taste from posterior 1/3

of tongue

Branchial Motor:Supplies styolopharyngeus

muscle

Cranial Nerve X: Vagus

Function General Sensory: posterior meninges, concha, skin at back of ear, external

tympanic membrane, pharynx & larynx

Visceral Motor: parasympathetic stimulation to smooth muscle &

glands of pharynx, larynx; thoracic & abdominal viscera & cardiac

muscle

Visceral Sensory: from larynx, trachea, esophagus, & thoracic &

abdominal viscera, stretch receptors & chemoreceptors

Motor: superior, middle, inferior constrictors; levator palati,

salpingopharyngeus, palatopharyngeus, palatoglossus

Purpose of the test To test the elevation of palate & contraction

of pharynxTo examine the movts of vocal cords

[note: the IX & X nerve are tested together]

Method of testing Notice the pitch & quality of voice, cough &

difficulty in swallowing saliva Ask the Pt to open his mouth wide after a few

movts ask to say “AH” while breathing out & “UGH” while in

The palate should move symmetrically upwards & backwards, the uvula in mid line & two sides of pharynx contract symmetrically

Common causes of lesionPoliomyelitis SyringobulbiaPosterior fossa tumor Advanced parkinsonismMyasthenia gravis Enlarged cervical glandsSurgical operation of the neck

Cranial Nerve XI: Accessory

Function

Supplies sternocleidomastoid & trapezius muscles

Purpose of the test To detect wasting & weakness, unilateral or

bilateral of the muscles

Method of testing

Common causes of paralysisMNDPoliomyelitis PolyneuropathyTrauma in the neck or base of skullTumour at jugular foramenSyringomyelia

Cranial Nerve XII: Hypoglossal

Function Control movts of the tongue, hyoid bone &

larynx during & after deglutition

Supplies 3 of 4 extrinsic muscles of tongue &

all intrinsic muscles of tongue

Purpose of the test To inspect the surface of the tongueTo detect wasting, weakness & involuntary

movtsTo examine voluntary muscle control

Method of testing Ask the Pt to protrude the

tongue & observe for • Reduction in size of affected side

• Excessive ridging & wrinkling

• Restricted protrusion

• Deviation towards one side

Common lesions Syringomyelia Poliomyelitis MND Profound hemiplegiaALS

13th Cranial Nerve

Known as cranial nerve zero or Terminal Nerve

It projects from nasal cavity, enters brain just a little bit ahead of other cranial nerves as a microscopic plexus of unmyelinated peripheral nerve fascicles

Function

The nerve is vestigial or related to sensing of pheromones

Regulates sexual behavior in mammals