Download Cranial nerves

High Yield Cranial
Nerve Anatomy
● this only covers
info on
previous
exams
● CN I, XI, and
XII not tested
● typically 5
questions per
exam
CRANIAL NERVE TERMS:
Efferent
●
General efferent fibers (GVE or visceral efferent or autonomic efferent): provide motor
innervation to smooth muscle, cardiac muscle, and glands.. May be either sympathetic or
parasympathetic.
○
oculomotor nerve (CN III), facial nerve (CN VII), glossopharyngeal nerve (CN IX) and
vagus nerve (CN X).
●
Special visceral efferent (SVE) : provide motor innervations to the muscles of the
pharyngeal arches in humans and branchial arches in fish. Also called "branchiomotor",or
"branchial efferent".
○
trigeminal nerve (V), facial nerve (VII), glossopharyngeal nerve (IX), vagus nerve (X)
and the accessory nerve (XI).
●
General somatic efferent (GSE): motor innervation to skeletal muscle.
AFFERENT:
● general visceral afferent fibers (GVA): conduct sensory impulses (usually pain or reflex
sensations) from the viscera, glands, and blood vessels to the central nervous system.
○ Facial nerve (VII), the glossopharyngeal nerve (IX) and the vagus nerve (X).
● Special somatic afferent (SSA): carry information from the special senses of vision,
hearing and balance.
○ optic nerve (II) and the vestibulocochlear nerve (VIII).
● Special visceral afferent (SVA) : carry the special senses of smell (olfaction) and taste
(gustation).
○ olfactory (I), facial nerve (VII), glossopharyngeal nerve (IX) and the vagus nerve (X).
Optic nerve CN II
Special somatic afferent transmits visual information from the retina to the brain
fibers carrying information from the temporal visual field
which cross in the optic chiasm briefly bend up into the
contralateral optic nerve
a lesion of the optic nerve close to the chiasm interrupts all
the fibers from the ipsilateral eye and crossing fibers from
the contralateral eye
the optic nerve is NOT in the cavernous sinus (came up more
than once)
the optic foramen,transmits the optic nerve and ophthalmic
artery (with accompanying sympathetic nerve fibers) into the
orbital cavity.
Oculomotor CNIII
Somatic motor
(general somatic efferent)
supplies: levator palpebrae
superioris muscle of the
upper eyelid. Superior
rectus, inferior oblique and
inferior rectus
Visceral motor
(general visceral efferent)
Parasympathetic
innervation of the
constrictor pupillae and
ciliary muscles to change
the shape of the lens for
accommodation.
*Loss of the ciliary
ganglion will produce loss
of the direct pupillary reflex
and pupillary dilation
The oculomotor nerves pass between the proximal portions of the posterior cerebral and superior cerebellar
arteries
Trochlear nerve CN IV
Innervates the the superior
oblique
Paralysis results in extorsion
of the ipsilateral eye, diplopia
Head tilt away from the
affected side to compensate
Exits brainstem dorsally
Trigeminal CNV
The trigeminal nerve is
composed of three large
branches.
● ophthalmic (V1, sensory)
● maxillary (V2, sensory)
● mandibular (V3, motor and
sensory)
● Innervation of the dura
within the cranial vault is
provided by the ophthalmic
branch (V1)
Trigeminal
V3 branch of the trigeminal nerve
supplies the muscles of mastication:
- temporalis, masseter, medial and
lateral pterygoids, mylohyoid,
anterior belly of the digastric,
tensor veli palatini, tensor tympani
Abducens CN VI
●
The abducens nerve emerges
from the ventral surface of the
brainstem between the pons
and medulla, most medial
●
Supplies the lateral rectus
●
In the cavernous sinus it runs
alongside the internal carotid
artery. It then enters the orbit
through the superior orbital
fissure and innervates the
lateral rectus muscle of the
eye.
Facial CN VII
Branchial motor
(special visceral
efferent)
frontalis, corrugator,
obicularis occuli, nasalis,
buccinator, obicularis
oris, mentalis, platysma
Visceral motor
(general visceral
efferent)
Parasympathetic
innervation of the
lacrimal, submandibular,
and sublingual glands,
as well as mucous
membranes of
nasopharynx, hard and
soft palate.
Special sensory
(special visceral
afferent)
Taste sensation from the
anterior 2/3 of tongue;
hard and soft palates.
General sensory
(general somatic
afferent)
General sensation from
the skin of the concha of
the auricle and from a
small area behind the
ear.
nervus intermedius
Branchial motor fibers (facial
expression) constitute the largest
portion of the facial nerve.
The remaining three components, are
bound in a distinct fascial sheath from
the branchial motor fibers. Collectively
these three components are referred
to as the nervus intermedius.
*An injury to the nervus
intermedius would spare facial
muscles
Visceral motor
(general visceral
efferent)
Parasympathetic
lacrimal, submandibular,
and sublingual glands,
mucous membranes of
nasopharynx, hard and
soft palate.
Special sensory
(special visceral
afferent)
Taste anterior 2/3 of
tongue; hard and soft
palates.
General sensory
(general somatic
afferent)
General sensation from
the skin
Facial nerve
Exits the skull at the stylomastoid
foramen
Gives off 3 branches before exiting
the stylomastoid foramen
greater superficial petrosal
(lacrimation)
nerve to the stapedius
chorda tympani (taste,
glands)
A lesion distal to the greater petrosal (or
geniculate ganglion) but proximal to the
stapedius muscle would cause weakness in the
muscles of facial expression, alter sublingual
and submandibular function, and cause loss of
taste to the anterior ⅔ of tongue, cause
hyperacusis, SPARES lacrimation
Geniculate Ganglion
●
Contains special visceral afferent cell
bodies (taste) and sensory fibers to
the external auditory canal and
tympanic membrane
●
The motor and the parasympathetic
portions of CN 7 pass through the GG
without synapsing
●
Zoster can reactivate in sensory
ganglia. Causes facial paralysis, +/hearing loss/vertigo (spread to CN8).
Rash seen on external acoustic
meatus and lateral tongue (Ramsay
Hunt syndrome type 2/herpes zoster
oticus)
sphenopalatine/pterygopalatine
ganglion
● The pterygopalatine ganglion
(Meckel's ganglion, nasal ganglion or
sphenopalatine ganglion) is a
parasympathetic ganglion found in
the pterygopalatine fossa.
● It is one of four parasympathetic
ganglia of the head and neck, the
others being the submandibular
ganglion, otic ganglion, and ciliary
ganglion.
Sensory root: derived from two sphenopalatine branches of the maxillary nerve
their fibers, for the most part, pass directly into the palatine nerves; a few, however, enter the ganglion, constituting its sensory root.
Parasympathetic root: derived from the nervus intermedius through the greater petrosal nerve.
he preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve synapse with neurons whose postganglionic
axons, vasodilator, and secretory fibers are distributed with the deep branches of the trigeminal nerve to the mucous membrane of the
nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and upper part of the pharynx.
also sends postganglionic parasympathetic fibers to the lacrimal nerve (a branch of the Ophthalmic nerve, also part of the trigeminal nerve)
via the zygomatic nerve, a branch of the maxillary nerve(from the trigeminal nerve), which then arrives at the lacrimal gland.
The nasal glands are innervated with secretomotor from the greater petrosal nerve. The palatine glands are innervated by the
nasopalatine,greater palatine nerve and lesser palatine nerves. The pharyngeal nerve innervates pharyngeal glands. These are all
branches of maxillary nerve.
Sympathetic root: sympathetic efferent (postganglionic) fibers from the superior cervical ganglion.
These fibers, from the superior cervical ganglion, travel through the carotid plexus, and then through the deep petrosal nerve.
sphenopalatine ganglion
●
the preganglionic
parasympathetic fibers from
the greater petrosal branch of
the facial nerve synapse with
neurons whose postganglionic
axons, vasodilator, and
secretory fibers are distributed
with the deep branches of the
trigeminal nerve to the mucous
membrane of the nose, soft
palate, tonsils, uvula, roof of the
mouth, upper lip and gums, and
upper part of the pharynx.
●
It also sends postganglionic
parasympathetic fibers to the
lacrimal nerve which then arrives
at the lacrimal gland.
vestibulocochlear nerve CN VIII
2 functions:
●
●
Innervation to the cochlea for hearing
○
cochlear nerve relays with the first
order sensory cells in the spiral
ganglion, which is in the base of the
spiral lamina.
○
terminates at the dorsal and ventral
cochlear nuclei
Innervation to the vestibule for acceleration
sense
○
The vestibular ganglion (scarpa) gives
Enters the brainstem at the
cerebellopontine angle
cochlear nuclei
● Cochlear nuclei are the most
distal structures along the
auditory pathway that when
lesioned would still result in a
unilateral sensorineural
hearing loss
● Lesions to auditory pathways
beyond the cochlear nuclei
would cause some degree of
bilateral deficit
Glossopharyngeal CN IX
Branchial motor (special visceral efferent) – supplies
the stylopharyngeus muscle.
General visceral efferent – derived from the Inf.
salivatory nucleus, provides parasympathetic
innervation of the parotid gland via the otic ganglion
General visceral afferent– carries visceral sensory
information from the carotid sinus and carotid body.
Special visceral afferent – provides taste sensation
from the posterior one-third of the tongue, including
circumvallate papillae.
General somatic afferent– provides general sensory
information from inner surface of the tympanic
membrane, upper pharynx, and the posterior one-third
Exits at the jugular
foramen
Vagus CN X
The vagus nerve is the tenth cranial nerve and provides the bulk of the
parasympathetic input to the gastrointestinal system and to the heart. It is a mixed
sensory/motor/parasympathetic nerve.
Motor (efferent) fibers project from:
nucleus ambiguus - branchial motor fibers > pharynx, larynx
dorsal motor vagal nucleus - parasympathetic motor fibres (visceral efferent) >
heart, lungs, GI tract
Sensory (afferent) fibers project to:
nucleus solitarius - visceral sensory (taste)
spinal trigeminal nucleus - general sensory (cutaneous)
Vagus CN X
Components
Function
Central
connection
Cell bodies
Peripheral distribution
Special visceral efferent
Swallowing,
phonation
Nucleus
ambiguus
Nucleus
ambiguus
Pharyngeal branches, superior and inferior laryngeal nerves
General visceral efferent
Involuntary muscle
and gland control
Dorsal motor
nucleus X
Dorsal motor
nucleus X
Cardiac, pulmonary, esophageal, gastric, celiac plexuses, and
muscles, and glands of the digestive tract
General visceral afferent
Visceral sensibility
Nucleus
tractus
solitarius
Inferior
ganglion X
Cervical, thoracic, abdominal fibers, and carotid and aortic
bodies
Special visceral afferent
Taste
Nucleus
tractus
solitarius
Inferior
ganglion X
Branches to epiglottis and taste buds
General somatic afferent
Cutaneous sensibility spinal
trigeminal
nucleus
Superior
ganglion X
Auricular branch to external ear, meatus, and tympanic
membrane
Baroreceptor reflex
helps regulate blood pressure by detecting changes via baroreceptors mostly in the carotid sinus and aortic arch
baroreceptors are activated by an increased blood pressure, decreasing the activity of the sympathetic branch of the
autonomic nervous system, leading to a relative decrease in blood pressure. Likewise, low blood pressure
activates baroreceptors less and causes an increase in sympathetic tone via "disinhibition"
information from the carotid sinus travels via the glossopharyngeal nerve, that from the aortic arch is carried by the
vagus
all baroreceptor afferents synapse in the nucleus tractus solitarius which then projects to the ventrolateral medulla
hypoglossal CN XII
carries axons of general somatic
efferent (GSE)
providing motor control of the
extrinsic muscles of the tongue;
genioglossus, hyoglossus,
styloglossus, and the intrinsic
muscles of the tongue
does not supply the palatoglossus
(vagus)
Cavernous sinus
The cavernous sinus transmits multiple cranial
nerves to the superior orbital fissure and
foramen ovale. These are:
In the lateral wall from superior to inferior:
oculomotor nerve
trochlear nerve
trigeminal nerve- ophthalmic
(V1) and maxillary (V2)
divisions.
abducens is in the carotid sheath
RANDOM FACTS
foramens
facial = stylomastoid foramen
vagus, glossopharyngeal, accessory = jugular
all of the cranial nerves categorized as general
somatic efferent (III, IV, VI, XII) exit the
brainstem medially
Eye Movements
Brainstem
high yield questions only, from last 8 years
of RITE exams
Wallenberg Syndrome
dorsolateral medullary syndrome
ischemia in the distribution of the posterior inferior cerebellar artery (PICA).
involves:
vestibular nucleus (nystagmus/vertigo)
inferior cerebellar peduncle (ipsilateral ataxia)
spinal trigeminal nucleus (facial numbness),
spinothalamic tract (pain/temp contralateral body),
descending ocular sympathetic pathways (Horners?),
nucleus ambiguus (dysphagia, hoarseness, gag).
Ipsilateral limb ataxia in this case is due to involvement of the left inferior
cerebellar peduncle.
Ocular lateropulsion in a Wallenberg syndrome is likely due to a lesion of the
olivocerebellar climbing fibers that gives rise to functional disinhibition of
cerebellar cortex and to increased inhibition of the deep cerebellar nuclei.
Pontine stroke
Pt presents with: right arm and leg weakness with fine touch deficits,
left facial paresis, diplopia on left lateral gaze
Left (medial) pontine infarct
occlusion of paramedian branch of basilar artery
The patient has a crossed paresis, with right arm and leg weakness
- corticospinal tract
left facial paresis - left facial nucleus?
Diplopia, with left lateral gaze - left abducens nucleus
Sensory deficits of fine touch on the right arm, trunk, and leg - left
medial lemniscus
Weber syndrome
Weber syndrome is a midbrain stroke syndrome (cerebral peduncle)
involves the fascicles of the oculomotor nerve resulting in an ipsilateral CN III palsy
contralateral hemiparesis.
Decerebrate posturing
A lesion below the level of the red nucleus
(rostral midbrain) but above the level of the
vestibulospinal and reticulospinal nuclei will
result in decerebrate posture(upper
extremity in pronation and extension and the
lower extremity in extension).
The reason for this is that the red nucleus
(and rubrospinal tract) output reinforces
antigravity flexion of the upper extremity.
When its output is eliminated then the
unregulated reticulospinal and
vestibulospinal tracts reinforce extension
tone of both upper and lower extremities
Parinaud syndrome (dorsal midbrain
syndrome)
The clinical features are:
upgaze paresis
nystagmus on attempted convergence
eyelid retraction
pseudo-Argyll-Robertson pupils:
large pupils with sluggish reaction to light
A lesion producing these findings occurs in the midbrain tectal region. It often occurs by extra-axial compression
on the quadrigeminal plate (particularly the superior colliculi). Pineal region masses as well as obstructive
hydrocephalus may also cause the syndrome.
Video:
http://www.kaltura.com/index.php/extwidget/preview/partner_id/797802/uiconf_id/27472092/entry_id/0_94uxo64
p/embed/auto?
Millard-Gubler syndrome, ventral pontine
syndrome
A unilateral lesion of the ventrocaudal pons
Symptoms include:
1.
Contralateral hemiplegia (sparing the face) due to pyramidal tract
involvement
2.
Ipsilateral lateral rectus palsy with diplopia that is accentuated when
the patient looks toward the lesion, due to cranial nerve VI involvement.
3.
Ipsilateral peripheral facial paresis, due to cranial nerve VII
involvement.
Palatal myoclonus
The patient with multiple sclerosis and "rhythmic clicking" in her ears has palatal myoclonus.
A lesion of the pathway connecting the red nucleus, central tegmental tract, inferior olivary nucleus, and dentate nucleus
results in palatal myoclonus.
Guillain-Mollaret triangle
One and a half syndrome
Ipsilateral eye has no horizontal movements and the contralateral eye is only able to abduct.
The clinical findings are a combination of a left intranuclear ophthalmoplegia (which prevents the left eye from adducting on rightward gaze with end-gaze
nystagmus of the abducting right eye) and a left abducens nuclear palsy (which produces an ipsilateral gaze palsy preventing the patient from looking left).
The only horizontal eye movement still possible, then, is abduction of the
right eye on rightward gaze.
This lesion must involve the left medial longitudinal fasciculus and left abducens nucleus.
MLF lesion
right MLF lesion
- can abduct the left eye on attempted gaze to the left
but the right eye cannot be adducted
- nystagmus in the left (abducting eye)
ocular tilt reaction
-
skew deviation
ipsilateral ocular torsion
ipsilateral head tilt (torticollis)
caused by a peripheral or brainstem lesion affecting otolithic pathways
nucleus ambiguus
-source of branchial outflow to laryngeal muscles
- contains motor neurons that supply striated muscles of
the palate, pharynx, and larynx
- disruption of this nucleus will impair phonation