AN3 06: Cranial Nerves (VII, VIII, IX, X, XI, XII)

How does the facial nerve (CN VII) exit the posterior cranial fossa?

facial nerve (CN VII) exits the posterior cranial fossa via the internal auditory meatus

as two roots - a motor (larger) and a sensory root (nervus intermedius)

What is the nervus intermedius?

nervus intermedius is in between CN VII and CN VIII as they come out from the cerebellopontine angle (CN VII is medial to CN VIII)

nervus intermedius is sensory but contains secretomotor (parasympathetic) fibers as well

With what nerve does nervus intermedius fuse with to form the geniculate ganglion?

nervus intermedius (CN VII) fuses with the facial nerve (CN VII motor root) to form the geniculate ganglion within the petrous temporal bone

geniculate ganglion formed by fusion of

nervus intermedius (sensory root of CN VII)

and

facial nerve (motor root of CN VII)

within the petrous temporal bone

Which branches does the facial nerve give off?

facial nerve (CN VII) gives off 3 branches

greater petrosal nerve
CN VII contribution to pterygopalatine ganglion

nerve to stapedius
sound dampening muscle

chorda tympani nerve
before stylomastoid foramen
enters tympanic cavity to join lingual nerve (CN V3)

branching of facial nerve (CN VII) takes place within the petrous temporal bone
into three branches

greater petrosal nerve
connects to pterygopalatine ganglion

nerve to stapedius
sound dampening muscle

chorda tympani nerve
joins lingual nerve (CN V3)

The facial nerve may also contribute sensory fibers to the auricular branch of the vagus nerve (CN X). T/F?

true

facial nerve (CN VII) may also contribute sensory fibers to the auricular branch of the vagus nerve (CN X)

as it crosses the facial canal above stylomastoid foramen

Where does the facial nerve exit the temporal bone?

facial nerve (CN VII) exits the temporal bone through the stylomastoid foramen

behind the styloid process

After the facial nerve exits the temporal bone, which branches does it give off?

after exiting via stylomastoid foramen, facial nerve (CN VII) gives off

posterior auricular nerve

branch to stylohyoid

branch to posterior belly of digastric

enters parotid gland to form parotid plexus

and the 5 terminal branches

What are the sensory and motor components of the facial nerve (CN VII)?

sensory
GSA - concha or auricle (sound)
SVA - taste from anterior 2/3rds of tongue and palate

motor
SVE - branchial motor innervation (including muscles of facial expression)
GVE - parasympathetic to lacrimal, submandibular, sublingual, oral, nasal glands

Which two major branches of the facial nerve (CN VII) carry special sensory fibers (SVA)?

chorda tympani
joins lingual nerve (CN V3)
innervates 2/3rds of tongue for taste and submandibular and sublingual salivary glands

(greater) petrosal nerve
joins deep petrosal nerve
to form nerve of pterygoid canal that joins pterygopalatine ganglion

Track the route of chorda tympani as it branches from facial nerve (CN VII)

chorda tympani branches from facial nerve
enters middle ear cavity
travels over superior margin of tympanic membrane
exits skull via petrotympanic fissure
enters infratemporal fossa
where it joins lingual nerve (CN V3)
continues to tongue

What are the two types of fibers carried by chorda tympani?

chorda tympani has 2 types of fibers

special sensory (SVA)
taste from anterior 2/3rd of tongue

parasympathetic fibers (GVE)
glandular innervation to submandibular, sublingual, lacrimal, nasal and oral glands

chorda tympani branches from facial nerve
enters middle ear cavity
travels over superior margin of tympanic membrane
exits skull via petrotympanic fissure
enters infratemporal fossa
where it joins lingual nerve (CN V3)
continues to tongue

Track the route of (greater) petrosal nerve as it branches from facial nerve (CN VII)

(greater) petrosal nerve branches from facial nerve
exits petrous temporal bone at hiatus
joins deep petrosal nerve (postganglionic sympathetic)
to form nerve of pterygoid canal
that joins pterygopalatine ganglion
splits into 3 branches of palatine nerves

What are the 3 branches of the palatine nerves?

palatine nerve branches (of pterygopalatine ganglion, CN V2)

greater palatine nerve
innervates hard palate

lesser palatine nerve
innervates soft palate

nasopalatine nerve
innervates anterior hard palate and septum of nose

special sensory afferents are distributed to CN V2 branches

greater palatine nerve
innervates hard palate

lesser palatine nerve
innervates soft palate

nasopalatine nerve
innervates anterior hard palate and septum of nose

Branches of trigeminal nerve (CN V) and branches of facial nerve (CN VII) are both involved in forming pterygopalatine and submandibular ganglia. T/F?

true

maxillary branch of trigeminal (CN V2) and facial nerve (CN VII) form the pterygopalatine ganglion

mandibular branch of trigeminal (CN V3) and facial nerve (CN VII) form the submandibular ganglion

Parasympathetic fibers (GVE) travel within two major branches - chorda tympani and greater petrosal nerve. T/F?

true

chorda tympani joins lingual nerve and goes to submandibular ganglion
secretomotor innervation to salivary glands

greater petrosal nerve joins deep petrosal nerve to form nerve of pterygoid canal that goes to pterygopalatine ganglion

Where do postganglionic (secretomotor) fibers from pterygopalatine ganglion go to?

postganglionic (secretomotor) fibers from pterygopalatine ganglion go to

lacrimal gland

glands of nose

glands in palate

glands of pharynx

Through what nerve do postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the lacrimal gland?

postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the lacrimal gland via

zygomatic nerve (CN V1)
responsible for tear production

Through what nerve do postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands of nose?

postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands of nose via

nasal nerves
responsible for nasal cavity mucosa

Through what nerve do postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands in palate?

postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands in palate via

greater palatine nerve
lesser palatine nerve
nasopalatine nerve

responsible for glandular secretion of palate mucosa

Through what nerve do postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands of the pharynx?

postganglionic (secretomotor) fibers from pterygopalatine ganglion go to the glands of the pharynx via

pharyngeal nerve
responsible for secretion of glands in superior pharynx

What is the clinical significance of bilateral innervation of muscles of upper face compared to unilateral innervation of contralateral lower face?

muscles of upper face are innervated by both sides of the primary motor cortex

muscles of lower face are innervated by contralateral primary motor cortex

a lesion of primary motor cortex on right side will paralyze left lower face but spare upper face

supranuclear lesion at A

contralateral weakness of lower face with relative sparing of upper face

neurons that innervate muscles of upper face receive bilateral corticobulbar innervation

can raise eyebrows and frown, but not smile on contralateral side

What would be expected from a lesion of the facial nucleus or nerve?

LMN signs
(lower motor nerve signs)

affects both upper and lower face
cannot frown, raise eyebrows or smile

What would be expected from a lesion of the cortex or corticobulbar fibers?

UMN signs
(upper motor nerve signs)

affects lower face only
can frown and raise eyebrows, but cannot smile

If patient can frown whole upper face but not cannot smile on one side of face, where would a potential lesion be located?

can frown - upper face innervated by both sides
cannot smile on one side - lower face innervated by one side only

potential supranuclear lesion

even though both nerves on one side cut, upper face still receives some innervation from ipsilateral side

If a patient can only frown on one side and smile on one side, where would a potential lesion be located?

cannot frown or smile on one side - upper face and lower face affected
no ipsilateral innervation of upper face as compensation

potential LMN lesion

despite upper face being innervated by both sides, the nerve was cut in lower section

What are the two divisions of the vestibulocochlear nerve (CN VIII)?

two divisions of the vestibulocochlear nerve (CN VIII) are

cochlear nerve
special sensory from cochlear for audition

vestibular nerve
sensory from vestibular apparatus for position and movement

Where does the vestibulocochlear nerve originate from?

How does it travel?

vestibulocochlear nerve (CN VIII) originates from the cerebellopontine angle (junction of medulla, pons and cerebellum)

enters petrous temporal bone via internal acoustic meatus

divides into cochlear and vestibular divisions in the meatus

What route does the cochlear nerve take from internal auditory meatus to spiral lamina?

cochlear nerve exits distal end of internal acoustic meatus to base of cochlea

enters cochlear via modiolus

neurons ascend within modiolus to base of spiral lamina

What is the spiral ganglion?

spiral ganglion contain cell bodies of bipolar cochlear neurons

distal processes of the cochlear neurons travel to the organ of Corti where they synapse with hair cells

What route does the vestibular nerve take from vestibular ganglion to vestibular apparatus?

vestibular nerve exits distal end of internal acoustic meatus to vestibular ganglion
(contains bipolar vestibular neurons)

after which, vestibular nerve branches into superior and inferior divisions

each division innervates parts of vestibular apparatus

Where do the glossopharyngeal nerve (CN IX) and vagus nerve (CN X) originate from?

glossopharyngeal nerve (CN IX) and vagus nerve (CN X) originate from

anterolateral aspect of medulla oblongata
(caudal brainstem, behind olivary eminence)

The apparent origin of glossopharyngeal nerve (CN IX) is rostral to that of vagus nerve (CN X). T/F?

true

both travel laterally through the posterior cranial fossa to exit cranium via the jugular foramen

(travels along with accessory nerve, CN XI)

The glossopharyngeal nerve is a mixed cranial nerve. T/F?

true, it has the following components

sensory
GSA - general sensory
GVA/SVA - visceral and special sensory

motor
SVE - branchial motor
GVE - visceral motor

Describe the general sensory afferents (GSA) of glossopharyngeal nerve (CN IX)

general sensory afferents (GSA) of glossopharyngeal nerve (CN IX)

carry sensory information from external ear

travels in auricular nerve

Describe the visceral and special sensory afferents (GVA/SVA) of glossopharyngeal nerve (CN IX)

visceral afferents from carotid body and carotid sinus

posterior 1/3rd of tongue, pharynx, pharyngotympanic tube, tympanic cavity

special sensory (taste) to posterior 1/3rd of tongue

Describe the branchial motor (SVE) of glossopharyngeal nerve (CN IX)

branchial motor (SVE) of glossopharyngeal nerve (CN IX)

motor to stylopharyngeus
between the styloid process and the pharynx

Describe the visceral motor (GVE) of glossopharyngeal nerve (CN IX)

visceral motor (GVE) of glossopharyngeal nerve (CN IX)

parasympathetic to the otic ganglion (parotid gland)

GSA - external ear

GVA - carotid body, carotid sinus

SVA - posterior 1/3rd tongue (taste)

SVE - stylopharyngeus

GVE - parasympathetic to otic ganglion and innervation to parotid gland

Glossopharyngeal nerve (CN IX) contains which two sensory ganglia?

glossopharyngeal nerve (CN IX) contain

superior and inferior petrosal ganglia of glossopharyngeal nerve

inferior ganglion contains cell bodies of GVA and SVA

superior ganglion contains cells bodies of GSA

Describe the course of the glossopharyngeal nerve (CN IX)

descends anterior to internal carotid artery
lateral aspect of stylopharyngeus
travels medial to hypoglossus
passes between superior and middle constrictor muscles
to reach posterior tongue and pharynx

tympanic branch
(= lesser petrosal nerve)

carotid sinus nerve

pharyngeal branches

nerve to stylopharyngeus

tonsillar branches

lingual branches

What does the tympanic nerve innervate?

tympanic nerve innervates

parasympathetic to the otic ganglion

sensory to the tympanic cavity

How does tympanic nerve travel from inferior ganglion to tympanic cavity?

tympanic nerve branches off at inferior ganglion
enters middle ear via tympanic canaliculus
forms tympanic plexus
GVE fibers enter lesser petrosal nerve
that enter cranium through roof of tympanic cavity

How does the lesser petrosal nerve travel from exiting cranium to innervate the parotid gland?

lesser petrosal nerve exits cranium via foramen ovale
fibers synapse in otic ganglion
postganglionic (secretomotor) fibers exit otic ganglion
join auriculotemporal nerve (CN V3)
to innervate parotid gland

Sensory fibers are distributed from the tympanic plexus providing innervation for the middle ear, pharyngotympanic tube, and mastoid air cells. T/F?

true

tympanic plexus distributes sensory fibers to

middle ear
pharyngotympanic tube
mastoid air cells

tympanic nerve innervates

parasympathetic to otic ganglion
sensory to tympanic cavity

forms tympanic plexus
to innervate middle ear, pharyngotympanic tube, mastoid air cells

synapse in otic ganglion
innervates parotid gland

Glossopharyngeal nerve (CN IX) and trigeminal nerve (CN V) form which ganglion of the head?

glossopharyngeal nerve (CN IX) and trigeminal nerve (mandibular nerve, CN V3) form otic ganglion

the 4 ganglion of the head are
ciliary ganglion
pterygopalatine ganglion
submandibular ganglion
otic ganglion

What is the function of the carotid sinus nerve?

carotid sinus nerve

monitors arterial blood pressure (baroreceptors)
carotid sinus

monitors blood O₂ and CO₂ levels (chemoreceptors)
carotid body

How does the carotid sinus travel?

carotid descends in front of internal carotid artery to innervate (GVA)

carotid sinus (baroreceptors)
blood pressure

carotid body (chemoreceptors)
blood O₂ and CO₂ levels

carotid body detects
blood O₂ and CO₂ levels
(chemoreceptors)

carotid sinus detects
blood pressure
(mechanoreceptors)

Describe pharyngeal branches of glossopharyngeal nerve (CN IX)

pharyngeal branches provide sensory to mucosa of pharynx

some ramifications of pharyngeal branches join pharyngeal branches of the vagus nerve (CN X) and cervical plexus to form pharyngeal plexus on posterior aspect of middle constrictor muscle

Describe the nerve to the stylopharyngeus (branch of glossopharyngeal nerve (CN IX))

nerve to stylopharyngeus provides motor innervation (SVE) to the stylopharyngeus muscle

stylopharyngeus is the only muscle innervated by CN IX

Describe the tonsillar branches of glossopharyngeal nerve (CN IX)

tonsillar branches provide sensory (GVA) to palatine tonsil and tonsillar pillars

Describe the lingual branches of glossopharyngeal nerve (CN IX)

lingual branches provide

sensory (GVA) from posterior 1/3rd of tongue

taste (SVA) from posterior 1/3rd of tongue and vallate papillae

lingual branches of the glossopharyngeal nerve (CN IX)

provide taste (SVA) sensation to posterior 1/3rd of tongue

Which two nerves (and origins) provide taste (SVA) sensation to the tongue?

whole tongue is innervated by

chorda tympani, of facial nerve (CN VII)

lingual branches of glossopharyngeal nerve (CN IX)

The vagus nerve (CN X) is a large mixed nerve with both motor and sensory components. T/F?

What components does it have?

true (vagus = "wandering")

sensory
general sensory (GSA)
visceral and special sensory (GVA, SVA)

motor
branchial motor (SVE)
visceral motor (GVA)

What is the general sensory afferent (GSA) of the vagus nerve (CN X)?

CN X - GSA
sensations from

external auditory meatus

dura mater
(of posterior cranial fossa)

What is the visceral sensory afferent (GVA) of the vagus nerve (CN X)?

CN X - GVA
sensations from

pharynx and larynx

thoracic viscera

abdominal viscera
(to left colic flexure)

carotid body

What is the special sensory afferent (SVA) of the vagus nerve (CN X)?

CN X - SVA
sensations from

taste afferents from epiglottis

extreme root of tongue
(just anterior to epiglottis)

What is the visceral motor efferent (GVE) of the vagus nerve (CN X)?

CN X - GVE
parasympathetic innervation to

heart

lungs

digestive tract
(to left colic flexure)

What is the special motor efferent (SVE) of the vagus nerve (CN X)?

CN X - SVE (branchial motor)
motor innervation to

soft palate
(except tensor veli palatini (CN V3))

pharynx
(except stylopharyngeus (CN IX))

larynx

upper 2/3rds of esophagus

How does the vagus nerve (CN X) exit the posterior cranial fossa?

vagus nerve (CN X) exits posterior cranial fossa via the jugular foramen

has two sensory ganglia located at and below jugular foramen

What and where are the two sensory ganglia associated with the vagus nerve (CN X) at and below the jugular foramen?

superior (jugular) ganglion
general somatic afferents (GSA)
that enter auricular nerve

inferior (Nodose) ganglion
general visceral afferents (GVA)
and some taste afferents (SVA)

Where does the accessory nerve (CN XI) merge with the vagus nerve (CN X)?

accessory nerve (CN XI) merges with the vagus nerve (CN X) immediately above the inferior ganglion

How does the vagus nerve (CN X) continue to travel after the inferior ganglion?

after the inferior ganglion

the vagus nerve (CN X) continues inferiorly within carotid sheath

between internal carotid artery and internal jugular vein

structures that go through jugular foramen

internal jugular vein

glossopharyngeal nerve (CN IX)

vagus nerve (CN X)

accessory nerve (CN XI)

internal carotid artery enters cranium by the carotid canal

List the branches of the vagus nerve (CN X) within the head and neck region after it is has passed through the jugular foramen

branches of the vagus nerve (CN X)

meningeal branch
auricular branch
pharyngeal branch
superior laryngeal nerve
cervical cardiac branches
recurrent laryngeal nerve

From which vagus nerve (CN X) ganglion does the meningeal branch arise?

meningeal branch of vagus nerve (CN X) arises from superior (jugular) ganglion and re-enters jugular foramen

sensations (GSA) from dura mater of posterior cranial fossa

From which vagus nerve (CN X) ganglion does the auricular branch arise?

auricular branch of vagus nerve (CN X) arises from superior (jugular) ganglion and enters mastoid canaliculus, traverses along temporal bone, through tympanomastoid fissure

sensations (GSA) from external ear and tympanic membrane

Auricular branch of vagus nerve (CN X) receives a communicating branch from inferior ganglion of glossopharyngeal nerve (CN IX). T/F?

true

auricular branch of vagus nerve (CN X) then enters mastoid canaliculus, traverses along temporal bone, through tympanomastoid fissure

sensations (GSA) from external ear and tympanic membrane

branches from superior ganglion

meningeal branch
re-enters jugular foramen
innervates (GSA) dura mater of posterior cranial fossa

auricular branch
enters mastoid canaliculus
exits tympanomastoid fissure
innervates (GSA) external ear and tympanic membrane

From which vagus nerve (CN X) ganglion does the pharyngeal branch arise?

pharyngeal branch of vagus nerve (CN X) arises from inferior ganglion and travels between external and internal carotid arteries

motor innervation (SVE) to

soft palate
(except tensor veli palatini (CN V3))

pharynx
(except stylopharyngeus (CN IX))

What branch does the pharyngeal branch of the vagus nerve (CN X) give, and what does it innervate?

nerve to carotid body is a branch of pharyngeal branch of vagus nerve (CN X)

innervates carotid body that detects O₂ and CO₂ levels (chemoreceptors)

From which vagus nerve (CN X) ganglion does the superior laryngeal nerve arise?

superior laryngeal nerve of vagus nerve (CN X) arises from inferior ganglion

sensory
visceral sensory (GVA) - larynx
taste (SVA) - extreme root of tongue and epiglottis

motor (SVE)
inferior pharyngeal constrictor
cricothyroid muscle

Which branches does superior laryngeal nerve branch divide into?

superior laryngeal nerve divides into

internal branch
pierces thyrohyoid membrane
sensory innervation

external branch
travels posterior to superior thyroid artery and vein
motor innervation

What does the internal branch of superior laryngeal nerve (of vagus nerve, CN X) innervate?

internal branch of superior laryngeal nerve
pierces thyrohyoid membrane

sensory innervation

root of tongue (taste - SVA)
epiglottis
larynx (above vocal folds)

What does the external branch of superior laryngeal nerve (of vagus nerve, CN X) innervate?

external branch of superior laryngeal nerve
travels posterior to superior thyroid artery and vein

motor innervation

inferior pharyngeal constrictor
cricothyroid muscle

nerve to carotid body is a branch of pharyngeal branch of vagus nerve (CN X)

innervates carotid body that detects O₂ and CO₂ levels (chemoreceptors)

How do the two branches of the cervical cardiac branches divide from the vagus nerve (CN X)?

two branches divide from vagus nerve to form cervical cardiac branches

superior and inferior branches

preganglionic parasympathetic (GVE) to cardiac plexuses

What do the recurrent laryngeal nerves innervate?

recurrent laryngeal nerves

sensory (GVA) to
larynx below vocal folds

motor (SVE) to
intrinsic muscles of larynx
(except cricothyroid - external branch of superior laryngeal nerve, CN X)

What is the the difference in recurrence between the left and right recurrent laryngeal nerves from vagus nerve (CN X)?

right recurrent laryngeal nerve
wraps under subclavian artery (1st segment)

left recurrent laryngeal nerve
wraps under and behind aortic arch

What do the recurrent laryngeal nerves innervate?

recurrent laryngeal nerve innervates larynx (voice box)

cricothyroid muscle is innervated by external branch of superior laryngeal nerve (CN X)

rest of intrinsic muscles of larynx are innervated by recurrent laryngeal nerves

The accessory nerve (CN XI) is traditionally considered to have which two parts?

accessory nerve has two parts

cranial root
considered to be part of vagus nerve

spinal root
originates in spinal accessory nucleus of ventral horn

The cranial root of accessory nerve (CN XI) has SVE fibers that contribute to pharyngeal and recurrent laryngeal branches. T/F?

true

cranial root of accessory nerve (CN XI) has SVE fibers that contribute to pharyngeal and recurrent laryngeal branches of vagus nerve (CN X)

therefore commonly considered to be part of vagus nerve (CN X)

How does the spinal root of accessory nerve (CN XI) exit the cranium?

spinal root of accessory nerve (CN XI) exits cranium through the jugular foramen and descends with internal jugular vein

motor innervation (GSE) of

sternocleidomastoid

trapezius

spinal accessory nerve (CN XI) exits cranium through the jugular foramen

other structures that go through jugular foramen are
internal jugular vein
glossopharyngeal nerve (CN IX)
vagus nerve (CN X)

From where on the brain stem does the hypoglossal nerve (CN XII) exit the brain stem?

hypoglossal nerve (CN XII) exits the brain stem between the pyramid and olivary eminence of medulla oblongata

How does the hypoglossal nerve exit the cranium?

hypoglossal nerve exits cranium through hypoglossal canal

What does the hypoglossal nerve (CN XII) innervate?

hypoglossal nerve innervates all muscles of tongue
except palatoglossus (CN X)

What branches come from the hypoglossal nerve (CN XII)?

hypoglossal nerve (CN XII) divides into

meningeal branch
re-enters hypoglossal canal
innervates dura mater of posterior cranial fossa

terminal branch
styloglossus
hypoglossus
genioglossus
and intrinsic tongue muscles

What does the meningeal branch of hypoglossal nerve (CN XII) innervate?

meningeal branch of hypoglossal nerve (CN XII) innervates

dura mater of posterior cranial fossa
by re-entering via hypoglossal canal

meningeal branch of vagus nerve (CN X) also innervates dura mater of posterior cranial fossa

What does the terminal branch of hypoglossal nerve (CN XII) innervate?

terminal branch of hypoglossal nerve (CN XII) innervates

styloglossus
hypoglossus
genioglossus
and intrinsic tongue muscles

AN3 06: Cranial Nerves (VII, VIII, IX, X, XI, XII)

Physician Assistant Pa 2013 Session 1 with Tsai at Touro University (NV)

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