Download Brainstem II

Tim McDowell
October 13, 2010
Objectives
 Overview the anatomy and function of CNs
 VII Facial
 VIII Vestibulococholar
 IX Glossopharyngeal
 X Vagus
 XI Spinal Accessory
 XII 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
foramenparotid gland
Facial Nerve Function
 Motor, parasympathetic, sensory functions
 Motor:
 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 Function
 Sensory:
 Taste for anterior 2/3 of tounge

chorda tympanageniculate ganglion
 Sensation of portion of external auditory meatus, lateral
pinnea and mastoid

greater superfical petrosal nerve geniculate ganglion
 Travel 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 Function
 Parasympathetic
 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)
Quiz
 Which of the following can cause a facial nerve palsy
 A Mobius syndrome
 B Millard-Gubler Syndrome
 C 8 ½ syndrome
 D Melkersson-Rosenthal syndrome
 E All of the above
Vestibulococholar Nerve
 Special sensory
function which
carries hearing and
vestibular sense
 Exits brainstem at
cerebellopontine
angle internal
auditory meatus 
auditroy canal 
cochlea + vestibular
organs
Vestibulococholar Nerve Anatomy:
Auditory
 Neuroepithelial 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 Pathways
 Dorsal 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 Pathways
 Commissural
connections between
superior olivary
complexes, cochlear
nuclei, nucleir of lateral
lemniscus, and inferior
colliculus
 Therefore unilateral
hearing loss is not
seen in CNS lesions
proximal to the
cochlear nuclei
Auditory Pathways
 3rd order neurons project from inferior colliculus to
medial geniculate body (thalamus)
 High-freq medial
 Low-freq apical-lateral
 Auditory radiation  white matter tract below
putamen  temporal lobe (primary auditory cortexBrodmann’s area 41> audiotry association cortex area
42)
 High-freq medial, low-freq lateral
Vestibulococholar Nerve Anatomy:
Vestibular
 Measures angular and linear acceleration of the head
within the membranous labyrinth
 3 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
+ utricle
 Inferior portion posterior semicircular canal + saccule
Vestibular Pathways
 Vestibular nerve projects to vestibular nuclei in
pontomedullary junction
 Superior (of Bechterew)
 Lateral (of Deiters)
 Medial (of Schwalbe)
 Inferior (descending nucleus of Roller)
 Semicircular canals  superior and medial nuclei
 Macular fibers medial and inferior vestibular nuclei
 Vestibular nerve also projects inferior cerebellar peduncle
 vestibulocerebellum (flocculonodualr lobes)
Vestibular Pathways
 Output primarily re: feedback integration with cerebellum,
spinal cord, and brainstem
 Main 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 cord
 Lateral 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?
 Latency
 Torsional, upper pole beats towards ground
 Fatigability
 Rebound
 Habituation
Glossopharyngeal Nerve Anatomy
 Emerges 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 Function
 Motor:
 stylopharyngeal muscle


Mildly lower palatal arch
Mild dysphagia
 Supplied from nucleus ambiguus
 Sensory:
 taste +sensation to post. 1/3 of tougne
 sensation to soft palate, tonsils, pharyngeal wall, tragus
of ear, eustachian tube, mastoid region
 Chemoreceptive and baroreceptive afferents from
caroitid body + sinus
Glossopharyngeal Nerve Function
 Sensory 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 Nerve
 Posterior 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 ear
 Meningeal ramusdura matter of post fossa
 Pharyngeal ramus  pharyngeal plexus (with IX)
 Superior laryngeal nerve (arises near nodose gangion):
sensory to larynx + cricothyroid muscle
Vagus Nerve
 In neck travels with internal carotid art + IJV)
 Cardiac rami: cardiac plexus
 Recurrent laryngeal nerves (left longer): all muscles of
larynx except cricothyroid
 Thorax: give off pulmonary and esphogeal plexus
 Abdomen: innervate abdominal viscera
Vagus Nerve
 Motor fibers originate from
 doral motor nucleus of vagus: preganglionic
parasympathetics
 nucleus ambiguus: striated muscles
 Sensory 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 Nerve
 Pure motor nerve
 Cranial root (becomes recurrent laryngeal nerve, mostly




travels with X)
Spinal root: dorsolateral portion of ventral horn in cervical
spinal cord (rostal portion SCM, caudaltrapezius)
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 Nerve
 Motor control of the tougne
 Arises from hypoglossal nucleus
 Exits medulla as multiple rootlets between pyramid
and inferior olivary nucleus  hypoglossal foramen
 NB UMN fibers cross before innervating hypoglossal
nuclei
Quiz:
 True or false
 Glossopharyngeal 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 foramen
 Common with glomus jugulare tumors and basal skull
fractures
Quiz
 Clincial picture of isolated VI and XII paresis:
 Godfresdsen syndrome
 Clival tumor, often nasopharyngeal, poor prognosis
TABLE 13-1 Syndromes Involving Cranial Nerves IX through XII
Other syndromes involving lower
CN’s
Syndrome (Eponym)
Collet-Sicard
Nerves Affected
Cranial nerves IX, X, XI, XII
Villaret's
Schmidt's
Cranial nerves IX, X, XI, XII
plus sympathetic chain; VII
occasionally involved
Cranial nerves X and XI
Jackson's
Cranial nerves X, XI, and XII
Tapia's
Cranial nerves X and XII
(cranial nerve XI and the
sympathetic chain occasionally
involved)
All cranial nerves on one side Often infiltrative; arising from
(often incomplete)
base of skull (especially
nasopharyngeal carcinoma)
Garcin's (hemibase syndrome)
Location of Lesion
Retroparotid space usually;
lesion may be intracranial or
extracranial
Retroparotid or retropharyngeal
space
Usually intracranial before nerve
fibers leave skull; occasionally
inferior margin of jugular
foramen
May be intraparenchymal
(medulla); usually intracranial
before nerve fibers leave skull
Usually high in neck