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Chris Evans

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Describe the origin, course, function,relevant pathology and integrity testsof cranial nerves 7-12

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Begins as 2 roots leaving brainstem laterallybetween the pons and medulla oblongata

Large motor rootsmall sensory root

(intermediate nerve)

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Pons

Medullaoblongata

Facial nerve leavesbrainstem between ponsand medulla oblongataon lateral sides

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3. Passes through facial canal in temporal bone4. Exits through stylomastoid foramen

Mastoid process

Stylomastoid foramen

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Gives offgreaterpetrosal nerve at thegeniculate ganglion Carries parasympathetic

fibres to lacrimal gland

Gives nerve tostapedius

Stapedius dampensexcessive movement ofstapes protects againstexcessive noise

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Gives chorda tympani joins with lingual nerve

(from mandibular nerve),provides parasympatheticinput to submandibular

and sublingual salivaryglands carries taste sensation

from anterior 2/3 oftongue

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Posterior auricularbranch suppliesposterior auricularmuscle and occipital

belly ofoccipitofrontalis

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Posteriorauricularbranch

Greater petrosal nerve

Facial CanalMotor root

Sensory root

Facial Nerve

Geniculate Ganglion

Nerve to stapediusChorda tympani

Stylomastoid Foramen Facial Nerve

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5. Enters parotidgland, splits into5 terminal motorbranches Temporal

Zygomatic

Buccal

Marginal mandibular

Cervical

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Innervates all muscles of facial expressionand anterior+posterior auricular muscles

Innervates stylohyoid, posterior belly ofdigastric and stapedius muscles

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Facial nerve is restricted inside bony facialcanal, and is vulnerable to compression ifinfection causes inflammation of the nerve

Damage to facial nerve may cause loss oftaste, inability to salivate and paralysis offacial muscles

Peripheral damage to facial nerve causes ipsilateral(same side) paralysis, damage to facial nerve in CNScasuses contralateral (opposite side) paralysis

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Ask patient to make aseries of different facialexpressions Make sure all muscles are

used and function correctly

Enquire about sense oftaste, mouth drynessand lacrimation

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Wrinkle forehead

Blow out cheeks

Close eyes against resistance

Bear teeth

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Consists ofvestibular andcochlear nerves that leavethe brainstem laterallybetween the pons andmedulla oblongata

The vestibular and cochlearjoin very soon after leavingbrainstem and enter theinternal acoustic meatus

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Pons

Medullaoblongata

Vestibulocochlear nerveleaves brainstem betweenpons and medullaoblongata on lateral

sides, just below facialnerve

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1. Crosses posterior cranial fossa2. Enters internal acoustic meatus

Internal acoustic

meatus

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3. Splits into vestibular and cochlear nerves

Cochlear nerve carries auditory information Forms spiral ganglion which connects to parts of the

cochlear

Vestibular nerve carries balance information Forms vestibular ganglion which connects to parts of the

vestibule

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Cochlear nerve

Vestibular nerve

Vestibulocochlear nerve

Cochlear nerve

Vestibular nerve

Internal acoustic meatus

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Posteriorauricularbranch

Cochlear nerve

Vestibular nerve

Vestibulocochlear nerve

Cochlear nerve

Vestibular nerve

Internal acoustic meatus

Greater petrosal nerve

Facial CanalMotor root

Sensory root

Facial Nerve

Geniculate Ganglion

Nerve to stapediusChorda tympani

Stylomastoid Foramen Facial Nerve

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Damage to the cochlear nerve can produceringing in the ears (tinnitus) or impairment ofhearing Damage to vestibular nerve can producedizziness and balance loss (vertigo) Central damage to CNVIII can produce a

combination of symptoms

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Conductive deafness problem with earprevents sound reaching cochlear (oftenmiddle ear inflammation)

Sensorineural deafness problem withcochlea/cochlear nerve prevents nerve signalsto brain

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Rinne test place a tuning fork on themastoid process, and then next to ear Second position should be louder identifiesconductive hearing loss Failure to hear either position shows sensorineuralhearing loss

Weber test place a tuning fork in middle offorehead Should be heard equally in both ears Detects unilateral hearing loss

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Begins on lateralaspect of medullaoblongata as severalrootlets, join in jugularforamen

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1. Crosses posterior cranial fossa2. Enters jugular foramen

Jugular foramen

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3. Forms the superiorand inferiorganglia aroundjugular foramen

4. Followsstylopharyngeus,terminates inoropharynx

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Supplies stylopharyngeus muscle Supplies parasympathetic fibres to parotidgland Conveys taste sensation from posterior 1/3of tongue Recieves information from carotid body

(chemoreceptor) and carotid sinus(baroreceptor)

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Recieves sensoryinformation fromposterior 1/3 of tongue

Sensory from oropharynx(tonsils, soft palate, backof throat)

Sensory from tympaniccavity, pharyngotympanictube and internal surfaceof tympanic membrane

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Isolated lesions of CNXI are uncommon Instead damage usually around jugular foramen andaffect multiple nerves (jugular foramen syndrome)

Lesions produce loss of taste and someproblems swallowing Gag reflex often lost

Absent in 1/3 of healthy people

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Touch arches of pharynx, testsensation Inquire about swallowing ability Check gag reflex

Stimulate back of tongue andoropharynx with tongue depressor

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Begins on lateralaspect of medullaoblongata below CNXIas several rootlets, joinin jugular foramen

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1. Crosses posterior cranial fossa2. Enters jugular foramen

Jugular foramen

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3. Forms a superiorand inferiorganglion belowjugular foramen

4. Continuesinferiorly incarotid sheath

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5. Give left and rightrecurrent laryngealbranches Right loops

around rightsubclavian artery Left loops aroundaortic arch

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Receives sensory input from: external auditory canal

skin posterior to ear

dura mater of posterior cranial fossa

Supplies all muscles of larynx Supplies pharyngeal muscles

Except stylopharyngeus Supplies muscles of soft palate

Except tensor velli pallatini

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Supplies parasympatheticmotor fibres to manythoracic and abdominalviscera

Receives sensory inputfrom viscera includingchemoreceptors andbaroreceptors in aorticarch

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Lesion causes deviation of palate towardsunaffected sided Muscles on healthy side have no opposition

Recurrent laryngeal branch lesions can causehoarseness of the voice and difficulty speaking

Can cause tachycardia and cardiac arrhythmias

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Check for palatal deviation Check ability to swallow

Have you had anything to drink today?

Listen to patients voice, inquire as to anychange

Listen for hoarseness, weakness, loss

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Begins as rootlets frommotor neurones of upper5 segments of spinalcord

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1. Ascends into cranial cavity, crossesposterior cranial fossa2. Enters jugular foramen

Jugular foramen

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3. Descends alongcarotid artery

4. Receives sensoryinput from cervicalplexus C2-4

5. Reachessternocleidomastoidand trapezius

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Provides motor input to sternocleidomastoidand trapezius Trapezius elevates and depresses shoulders, and

retracts scapula

Sternocleidomastoid rotates head and flexes neck Carries sensory information from SCM and

trapezius

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Relative superficial position near jugularvessels means it is susceptible to injuryduring surgical procedures

Damage produces weakness of SCM andtrapezius

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Ask patient to shrug shoulders and turn headagainst resistance

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Begins on lateralaspect of medullaoblongata as severalrootlets

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3. Receives motor andsensory fibres fromC1-2

4. Passes medial toangle of mandible,turns to reachtongue

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Innervates all intrinsic muscles of tongue, andall extrinsic muscles excluding palatoglossus

Supplies infrahyoid muscles

Sternohyoid Sthernothyroid Omohyoid

Meningeal branch returns to cranium throughhypoglossal canal and innervates dura inposterior cranial fossa

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Injury to hypoglossal nerve paralyses theipsilateral half of the tongue Causes atrophy on damaged side

Unopposed action of genioglossus causesdeviation towards damaged side Genioglossus protrudes tongue

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Examine tongue for wasting and fasiculations Small involuntary twitches

Damage causes deviation towards damaged side Deviation always caused by unopposed muscleaction!!

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