brainstem ii
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Tim McDowellOctober 13, 2010
ObjectivesOverview the anatomy and function of CNs
VII FacialVIII VestibulococholarIX GlossopharyngealX VagusXI Spinal AccessoryXII Hypoglossal nerve
Clinical cases and syndromes involving these nerves
Facial Nerve Anatomy
Course of Peripheral Nerve:Exits ventrolateral pons (CPA) internal auditory meatus facial canal in petrous bone geniculate ganglion stylomastoid foramenparotid gland
Facial Nerve FunctionMotor, parasympathetic, sensory functionsMotor:
Originate in motor facial nucleus (caudal pontine tegmentum)
Brachial motor branches control muscles of facial expression Temporal, zygomatic, buccal, mandibular, and cervical Branch off after parotid gland
Innervates stapedius muscle Branches shortly after geniculate ganglion in mastoid
segment
Facial Nerve FunctionSensory:
Taste for anterior 2/3 of tounge chorda tympanageniculate ganglion
Sensation of portion of external auditory meatus, lateral pinnea and mastoid greater superfical petrosal nerve geniculate
ganglionTravel as Nervus Intermedius of Wrisberg,
receives fibers from geniculate ganglion then travels to rostal nucleus solitarius (taste), and nucleus of the spinal tract of CN V (exteroceptive)
Facial Nerve FunctionParasympathetic
Originate in superior salivatory and lacrmial nucleus (pontine tegmentum)
Travel along nervus intermedius to: Sphenopalatine ganglion (lacrimal glands, nasal
glands) Submandibular ganglion (sublingual gland,
submandibular gland)
QuizWhich of the following can cause a facial
nerve palsyA Mobius syndromeB Millard-Gubler SyndromeC 8 ½ syndromeD Melkersson-Rosenthal syndromeE All of the above
Vestibulococholar NerveSpecial sensory
function which carries hearing and vestibular sense
Exits brainstem at cerebellopontine angle internal auditory meatus auditroy canal cochlea + vestibular organs
Vestibulococholar Nerve Anatomy: AuditoryNeuroepithelial hair cells stimulated by
endolymph causing movement of basilar membrane Cell body spinal ganglion of the cochlear nerve cochlear nuclei (dorsal and ventral) in the lateral medulla
Tonotopic pattern:Low frequencies (apex of cochlea ventral
nuclei)High frequencies (basal hair cells dorsal
nucleus)
Auditory PathwaysDorsal cochlear
nucleus dorsal acoustic striae (decussication) lateral lemniscus inferior colliculus
Ventral cochlear nuclei ventral acoustic striae (trapezoid body)superior olivary nucleus lateral lemniscus IC
Auditory PathwaysCommissural
connections between superior olivary complexes, cochlear nuclei, nucleir of lateral lemniscus, and inferior colliculusTherefore unilateral
hearing loss is not seen in CNS lesions proximal to the cochlear nuclei
Auditory Pathways3rd order neurons project from inferior
colliculus to medial geniculate body (thalamus) High-freq medialLow-freq apical-lateral
Auditory radiation white matter tract below putamen temporal lobe (primary auditory cortex- Brodmann’s area 41> audiotry association cortex area 42)High-freq medial, low-freq lateral
Vestibulococholar Nerve Anatomy: VestibularMeasures angular and linear acceleration of the
head within the membranous labyrinth3 Semicircular canals (angular, measured by cristae
inside the ampulla): horizontal, anterior/superior, posterior/inferior
Utricle and saccule (linear, measured by maculae which contain otolith crystals)
Afferent connection to cell bodies of vestibular ganglion of Scarpa (inside internal acoustic meatus)Superior portion: anterior and horizontal semicircular
canals + utricleInferior portion posterior semicircular canal + saccule
Vestibular PathwaysVestibular nerve projects to vestibular nuclei in
pontomedullary junctionSuperior (of Bechterew)Lateral (of Deiters)Medial (of Schwalbe)Inferior (descending nucleus of Roller)
Semicircular canals superior and medial nucleiMacular fibers medial and inferior vestibular nucleiVestibular nerve also projects inferior cerebellar
peduncle vestibulocerebellum (flocculonodualr lobes)
Vestibular PathwaysOutput primarily re: feedback integration with
cerebellum, spinal cord, and brainstemMain connectinos:
Medial Longitudinal Fasciculus (conjugate eye mvmts) Superior vestibular n.ipsilateral All others contralateral
Medial Vestibulospinal Tract (descending MLF) Mostly medial vestibular nucleus cervical and upper
thorasic contralateral spinal cordLateral Vestibulospinal Tract (facilitates extensor
trunk tone + antigravity muscles) Lateral + inferior vestibular nuclei ipsilateral spinal cord
Cerebellum Ipsilateral flocculondular lobe + reciprocal connection
back thru juxtarestiform body
Weber test: vibration at vertex, localizes to conductive hearing deficit and away from sensorineural hearing deficit
Rinne Test: air/bone cunduction compared in each ear
Dix-Hallpike:
Quiz:What makes a Dix-Hallpike Positive in BPPV?
LatencyTorsional, upper pole beats towards groundFatigabilityReboundHabituation
Glossopharyngeal Nerve AnatomyEmerges from
posterior lateral sulcus of medulla Jugular foramen widens to superior and petrous ganglia descends on lateral side of pharynx around stylopharyngeus muscle (+innervates) base of tougne
Glossopharyngeal Nerve FunctionMotor:
stylopharyngeal muscle Mildly lower palatal arch Mild dysphagia
Supplied from nucleus ambiguusSensory:
taste +sensation to post. 1/3 of tougne sensation to soft palate, tonsils, pharyngeal wall,
tragus of ear, eustachian tube, mastoid regionChemoreceptive and baroreceptive afferents
from caroitid body + sinus
Glossopharyngeal Nerve FunctionSensory Function continued
For taste + chemo/baro receptors, cell bodies in petrous ganglion, project to solitary nucleus (rostal: taste, caudal: chemo/baro receptors)
Exteroreceptive afferents, cell bodies in both petrous and superior ganglia spinal nucleus of V
Parasympathetic:Inferior salivatory nucleus otic ganglion
(synapse here) (Via V3) parotid gland
Vagus NervePosterior sulcus of lateral medulla, multiple
rootlets trunk, exits via jugular foramen Two vagal ganglia here: jugular (sup) + nodose
(inf)Auricular ramus branches off concha of external
earMeningeal ramusdura matter of post fossaPharyngeal ramus pharyngeal plexus (with IX)Superior laryngeal nerve (arises near nodose
gangion): sensory to larynx + cricothyroid muscle
Vagus NerveIn neck travels with internal carotid art +
IJV)Cardiac rami: cardiac plexusRecurrent laryngeal nerves (left longer): all
muscles of larynx except cricothyroidThorax: give off pulmonary and esphogeal
plexusAbdomen: innervate abdominal viscera
Vagus NerveMotor fibers originate from
doral motor nucleus of vagus: preganglionic parasympathetics
nucleus ambiguus: striated musclesSensory fibers:
Taste from epiglottis, hard & soft pallates, and pharynx, + general visceral afferents from oropharnyx, larynx, thorax and abdo viscera solitary nucleus (cell bodies in nodose ganglia)
Exteroreceptive sensation from ear spinal nucleus of V (cell bodies in juglar ganglion)
Spinal Accessory NervePure motor nerveCranial root (becomes recurrent laryngeal nerve,
mostly travels with X)Spinal root: dorsolateral portion of ventral horn
in cervical spinal cord (rostal portion SCM, caudaltrapezius)
Exit cord between ventral and dorsal nerve rootlets, just dorsal to dentate ligament
Ascend together into skull through foramen magnum exits via jugular foramen neck to supply SCM and trapezius
NB: UMN innervation of SCM is ipsilateral
Hypoglossal NerveMotor control of the tougneArises from hypoglossal nucleusExits medulla as multiple rootlets between
pyramid and inferior olivary nucleus hypoglossal foramen
NB UMN fibers cross before innervating hypoglossal nuclei
Quiz:True or falseGlossopharyngeal neuralgia is commonly
associated with MS?FALSE
The most common cause of isolated CN XI is iatrogenic?TRUE
Quiz:Clinical picture of:
Ipsilateral trapezius and sternocleidomastoid paresis and atrophy
Dysphonia, dysphagia, depressed gag reflex, and palatal droop on the affected side associated with homolateral vocal cord paralysis, loss of taste on the posterior third of the tongue on the involved side, and anesthesia of the ipsilateral posterior third of the tongue, soft palate, uvula, pharynx, and larynx
Often dull, unilateral aching pain localized behind the ear
Name the lesion. Where is it? Common causes?
Vernet’s Syndrome (Jugular Foramen Syndrome)Lesion at jugular foramenCommon with glomus jugulare tumors and
basal skull fractures
QuizClincial picture of isolated VI and XII paresis:
Godfresdsen syndromeClival tumor, often nasopharyngeal, poor
prognosis
Other syndromes involving lower CN’s
Syndrome (Eponym) Nerves Affected Location of LesionCollet-Sicard Cranial nerves IX, X, XI, XII Retroparotid space usually;
lesion may be intracranial or extracranial
Villaret's Cranial nerves IX, X, XI, XII plus sympathetic chain; VII occasionally involved
Retroparotid or retropharyngeal space
Schmidt's Cranial nerves X and XI Usually intracranial before nerve fibers leave skull; occasionally inferior margin of jugular foramen
Jackson's Cranial nerves X, XI, and XII May be intraparenchymal (medulla); usually intracranial before nerve fibers leave skull
Tapia's Cranial nerves X and XII (cranial nerve XI and the sympathetic chain occasionally involved)
Usually high in neck
Garcin's (hemibase syndrome) All cranial nerves on one side (often incomplete)
Often infiltrative; arising from base of skull (especially nasopharyngeal carcinoma)
TABLE 13-1 Syndromes Involving Cranial Nerves IX through XII
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