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DISORDERS OF CRANIAL NERVES

BY

Dr. Puji Pinta O. Sinurat, Sp S.

Neurology Departement/ Medical Faculty Sumatera Utara University

MEDAN

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The Cranial Nerves 12 pairs refer to by either name or

Roman numeral

- N I & N II : fiber tracts of the brain (not true nerves)

- N XI : derived, in part, from the upper cervical segment of spinal cord.

- The remaining nine pairs : relate to the Brain Stem

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FUNCTIONAL ORGANIZATION OF THE CRANIAL NERVES

Nerve Function Cr. NerveSensory I, II, VIIISomatic motor IV, VI, XI, XIISomatic motor & sensory VSomatic motor & parasymph III Somatic motor,sensory & parasympathetic VII, IX, X

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Cranial Nerve I : Olfactory Nerve- Function : Smell

- The true N I : short connect. from olfactory mucosa (nose) & olfactory bulb (cranial cavity)

- Lie just above cribiform plate and below the frontal lobe

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- Axons from olfac bulb olfact tract primary olfact cortex (pyriform cortex), entorhinal cortex and amygdala.

- Note : olfact impuls reach the cerebral cortex without relay through thalamus (a unique feature among the sensory system)

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Clinical Correlation :

- Anosmia = absence of the sense of smell- Dysosmia / Parosmia = distorsion of odor

perception (ex : empyema nasoph)- Olfactory hallucination: temporal lobe seizure

(“uncinate fits”), Alzeimer dementia- Olfactory agnosia loss of olfactory

discrimination

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ANOSMIA- the most clinical abnormality- Etiology :

* nasal : common cold, chr rhinitis, smoking* olfactory neuroepithelial : head injury tearing of filament, cranial surgery, toxic (certain drugs) * central (olfact pathway lesion): degenerative disease, Temporal lobe epilepsi, frontal lobe tumor, olfactory groove meningioma

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- Unilateral anosmia suggest compression of the olfac bulb/tract by frontal lobe glioma, abscess, olfact groove meningioma, sphenoid ridge meningioma and pituitary & parasellar tumor.

Tumor compress ipsilateral optic nerve optic atrophy

ICP ↑ papiledema contralaterally

Unilateral anosmia + ipsilateral optic atrophy & contralateral papiledema FOSTER-KENNEDY SYNDROM

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Cranial Nerve II : Optic Nerve

- Function : Vision- arises from gangl cells in the retina

thrgh optic papilla to the orbit (within meningeal sheaths) optic chiasm optic tract (its axons) project to Sup Coll & lat genicl bodies within the thalamus (relays visual information) calcarine cortex in the occipital lobe.

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Clinical correlationImpaired vision in one eye ---- usually due to involving the eye, retina, or optic nerveIf the lesion is in the opt chiasm, opt tract, or visual cortex field defect in both eyesChiasmatic lesion (axons originate in the nasal halves of the two retina) Bitemporal hemianopia (charact : blindness in the lateral or temporal half of the visual field for each eye)

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Opt tract lesion homonimous hemianopia (defect of temporal field of one eye + nasal field of the other eye) in wich the visual field defect is on the opposite side to the lesion.

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• Optic neuritis = inflammation of the optic nerve ----- is associated with various forms of retinitis such as simple, syphilitic, diabetic, hemorrhagic and hereditary

• Papilledema ------ usually a symptom of increased ICP caused by a mass (eg, brain tumor) transmitted to optic disc thrgh extension of subarachnoid space around the optic nerve.

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• Optic Atrophy ---- Is pallor of the optic

disc (change in color to light pink, white or gray) due to demielination and axonal degeneration of the optic n. - decrease visual acuity - Etio : tabes dorsalis, multiple sclerosis,

inherited

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• Primary optic atrophy:- occurs without preceding papiledema - by a process that involves the optic n. -Disc typically : uniformly white with clearly outlined margin

* Secondary optic atrophy:- is a sequel of papiledema - disc is white, but the margins are grayish

and indistinct

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- Axons arise in the oculomotor nuclei innerv levator of the eyelid, sup, inf & med recti, inf oblique.

- The parasympathetic nucl portion of oculomotor nucl (Edinger-Westphal nucl) innerv pupillary spinchter and the ciliary bodies (muscle of accomodation)

- Enters the orbit trough Sup Orbital Fissure

Cranial Nerve III : Oculomotor Nerve

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Cranial Nerve IV : Trochlear Nerve

- Nuclei : trochlear nucleus - Enters the roof of orbit through the Sup

Orbital Fissure- Innerv : Superior oblique muscle

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Cranial Nerve VI : Abducens Nerve

Nuclei : Abducens nucleusEnters the orbit through Sup orbital Fissure Innerv : Lateral rectus mIts long intracranial course vulnerable to pathologic processes in Posterior & midle Cranial fossa.

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The Cr nerves III, IV and VI control eye movements. In addition, Cr N III controls pupillary constriction.Note : m. Levator palpebrae Sup has no action on the eye ball, but lifts the upper eye lid when contractedClosing the eyelids by contrct of orbicular m of the eye (innerv by N VII)

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Clinical correlationThe eyes are normally positioned the image falls on exactly the same spot on the retina of each eye.Both eyes move in the same direction to follow an object in space, but they move by simultaneously contracting and relaxing different muscles The symmetric and synchronous movement of the eyes is called Conjugate or Gaze movement (conjugate = joined together)

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The slight displacement of either eye Diplopia (double vision)Strabismus : deviation of one or both eyesPtosis (lid drop) is caused by weakness or paralysis of the levator palp sup m.Opthalmoplegia : paralysis of cranial nerves III, IV and VI

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a. Oculomotor (N III) paralysis : 1. External Opth : - divergent strabismus - diplopia - ptosis2. Internal Opth : - dilated pupil - loss of light & accomodation reflexes

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b. Trochlear ( N IV) paralysis - slight convergent strabismus - diplopia on looking downward.(cannot look downward & inward difficulty in descending stairs tilted the head as a compensatory adjustment)

c. Abducens (N VI) paralysis - the most common eye palsy (owing to the long course of N VI). - convergent strabismus - diplopia.

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Cranial Nerve V : Trigeminal Nerve

The largest cranial nerveIs a mixed sensory and motor nerve :- Sensory root (large) carries sensation

from skin & mucosa of most head- Motor root (smaller) innerv chewing m

(massetter, temporalis, pterygoids, mylohyoid) and tensor tympani m of middle ear. Nucleus : in the Pons

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Sensory root

- arise from cells in the semilunar (Gasserian, Trigeminal) ganglion

- Contain 3 division Fibers:1. Opthalmic div enters the skull thrgh Sup Orbital Fissure lateral wall of cav sinus 2. Maxillary div enter the skull through For Rotundum lower lateral of cav sinus 3. Mandibular div enter the skull thrgh For Ovale (with the motor fibres) passed inf to cav sinus

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* Corneal Reflex - afferent : N V ( opthalmic div) - efferent : N VII

* Jaw jerk reflex : Its aff & eff run in N V.

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Clinical correlation

- loss of sensation 1 sensory modalities- paralysis m tensor tympani => impaired

hearing- Paralysis of mastication m => mandibular dev

to the affected side- Loss of reflex (corneal, jaw jerk)- Trismus (lock jaw)- Tonic spasm of the muscles of mastication

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TRIGEMINAL NEURALGIA (TIC DOULOUREUX, PAROXYSMAL FACIAL PAIN)

Def : a cond charact by sudden, severe, lancinating pain occuring in the distr of 1 div of N V.

Epid : 2-8/100.000/year. Female > Male

Etio : Idiopathic (most common cause), compression of N V root (eg, tumor), demyelination, etc

Clin features : Pain Site : face or mouth (commonly V2 or V3 div) Trigger factors : talking, chewing, swallowing, shaving,

cleaning the teeth, wind blowing on the face

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Trigger points : area around the nose, lips or mouth

Nature : stabbing/ligthning or electric shock-like/ penetrating or cluster of stabbing pain

Duration : brief (seconds) and followed by long pain-free intervals

Episodic pattern : may recur many times a day and may remit

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Physical Exam :- Normal in Idiophatic Trig Neuralgia- Secondary causes underlying cause

Investigation : CT/ MRI brain scanDiagnosis : ClinicalTreatment:- most patient can be managed medically

(carbamazepin, Phenytoin, baclofen etc)- Surgically

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Cranial Nerve VII : Facial Nerve

Consist of facial nerve proper & nervus intermedius

Axons of Facial n proper arise in the facial nucleus thrgh stylomast foramen innerv muscl of facial expression, m.platysma and stapedius m in the inner ear.

Nervus Intermedius sends parasympathetic pregangl fibres to pterygopalatine gangl innerv Lacrimal gld, and Via chorda tympani nerve to the submaxillary & sublingual ggln innerv salivary gld

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- Visceral aff fibres of n. Intermed carries taste sensation from the anterior 2/3 of the tongue, via chorda tympani & lingual nerve to solitary nucleus.

- Somatic afferent fibres from skin of ext ear carried in the N VII brain stem

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Clinical correlation

Facial nucl receives crossed & uncrossed fibres by way of corticobulbar (corticonuclear) tract. frontalis & orbic oculi m receives bilat cortical innerv not paralyzed by lesion in one motor cortex or its corticobulbar pathway

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Peripheral facial paralysis (Bell’s palsy) => attempt to close the eyelid the eye ball may turn upward (=bell’s phenomenon).Symptoms & signs depend on the location of the lesion : Lesion in or outside the For stylomast flaccid paralysis of facial expression m in the affected side.

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Lesion in the facial canal involving chorda tympani nerve reduced salivation and loss of taste sensation of 2/3 ant ipsilat of the tongue.Lesion higher up in the canal paralyze m stapedius.

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Is a double nerveArise from spiral and vestibular ganglia in the labyrinth of the inner ear.Passes into cranial cav via internal acoustic meatus the brain stemCochlear nerve hearing (audition)Vestibular nerve part of equilibrium (position sense)

Cranial Nerve VIII : Vestibulocochlear nerve

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Clinical correlationDEAFNESS = hearing loss

- Conduction deafness impairment of sound thrgh ext ear canal to endolymph and tectorial membrane.caused by mid or ext ear disease

- Nerve (sensoryneural) deafness caused by interrupt of cochlear nerve fibres from the hair cells to the brainstem nuclei (located : inner ear / cochlear n in the int auditory meatus)

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TINNITUS : ringing, buzzing, hissing, roaring or “paper-crshing” noises in the ear - frequently an early sign of peripheral cochlear diseaseNYSTAGMUS : involuntary movement (back-and-forth, up-and-down, or rotating) of the eyeballs

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VERTIGO : an illusory feeling of giddiness with disorientasi of space.- usually the results in a disturbance of equilibrium- often a sign of labyrinthine disease originating in the middle or int earBENIGN PAROXYSMAL POSITIONAL VERTIGO episodic rotational vertigo of brief duration induced by head movement

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MENIERE SYNDROME :- Recurrent episode of severe vertigo

associated with unilateral hearing loss and tinnitus

- spontaneous recovery within hours or days

- also known as endolymphatic hydrops

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Contains several types of fibers- Branchial efff fibr from nucl ambiguous pass to m.

Stylopharyngeus - Visceral eff fibr from nucl salivatory Inf pass trough

tympanic plexus & petrosal nerve to the otic ggln- Visceral aff fibr arise from unipolar cell in the

Inferior ganglia : carry taste sens from post 1/3 of the tongue

- Centrally : terminate in solitary tract and its nucleus project to thalamus cortex

Cranial Nerve IX : Glossopharyngeal Nerve

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Peripherally: visceral aff axons of N IX supply general sensation to the pharynx, soft palate, 1/3 post of the tongue, tonsil, auitory tube, and tympanic cavity. N IX supply special receptor in the carotid body and carotid sinus control of respiration, blood pressure and heart rate.

.

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Clinical correlationPharyngeal (gag) reflex depends on N IX

for its sensory components (N X innerv motor component).

Carotid sinus reflex depends on N IX for its sensory comp.

Pressure over the sinus => slowing of Heart rate and fall in BP.

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Glossopharyngeal neuralgia

Is the occurrence of spasm of pain in the sensory distribution of the IX & X cr nerne.Etio : unknown pressure or entrapment of the IX & X cr nerve Cl features : - spasm of pain in the pharynx, often radiating

into the ear. - Trigger point : in the throat. - Duration : brief. - Remission is common.

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Attack : associated with bradycardia, cardiac arrhytmia, hypertension and syncope ( due to vagal stimulation)Diagnostic Procedure: MRI / CT scanTreatment : determined by the cause respon to Carbamazepin.

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* Branchial eff fibr from nucl ambiguous pass to

the muscle of soft palate and pharynx via recurrent laryngeal nerve to intrinsic muscl of

larynx

* Visceral eff fibr from dorsal motor nucleus of the vagus => to thoracic & abdominal viscera

Cranial nerve X : Vagus Nerve

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• Somatic aff fibr of unipolar cells in Superior ganglion send peripheral branch via auricular branch of n X to the Ext auditory meatus & part of the earlobe.

• Visceral aff fibr of unipolar cells in Inferior ganglion send peripheral branch to the pharynx, larynx, trachea, esophagus, and thoracic & abdominal viscera.

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Clinical correlation Complete bilateral transection of vagus :

Fatal Weakness / paralysis of vocal cord =>

difficulty in swallowing and cardia arrhythmias.

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2 components : 1. Cranial component 2. Spinal component

Cranial components :distributed in the pharyngeal and recurrent laryngeal branches of the N X.

Spinal components :Motor to sternclmast and upper part of trapezius

Cranial Nerve XI : Accessory Nerve

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Clinical correlationUnilateral LMN lesion weaknes of ipsilat sternoclmast and upper part of trapeziusUMN lesion weaknes of ipsilat sternoclmast and upper part of contralat trapezius m. So that the patient cannot elevate the shoulder of paralyzed arm nor turn the head to wards the paralyzed side.

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The motor nerve to the tongue

Leaves the skull through hypoglossal canal distributing branches to all muscles of the tongue

Cranial Nerve XII : Hypoglossal Nerve

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Clinical correlationLMN Hypoglossal Nerve palsy :- Unilateral : mild dysarthria, wasting, fasciculation & weakness of one side of the tongue (ipsilateral to the lesion) with tongue dev to opposite side, Laringeal shift to one side on swallowing (contralat to the lesion)- Bilateral : difficulty manipulating food in the mouth, flaccid dysarthria (difficulty speaking)

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UMN Hypoglossal Nerve palsy:- Unilateral : mild dysarthria, mild tongue weakness contralat to the side of the UMN lesion, Usually transient- Bilateral : Severe dysarthria, spasticity of the tongue slow movement

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