Download 09. cranial N.nuclei2010-10-01 05:142.8 MB

Cranial nerves & Cranial nerve nuclei
There are 12, paired cranial
:
nerves.
The first 2 cranial Ns. attach
directly to forebrain, while the rest attach
to brain stem.
Olfactory system is attached to
forebrain and is referred to as the limbic
system, / optic N. also is discribed in
visual pathway.
The base of the brain showing
locations of cranial nerves
Cranial Ns. from 3 - 12 have
nuclei (cranial N.nucluei) in the
brain stem , receiving afferents Fs. Or
send efferent Fs. as the cranial Ns.
Superficial attachements of Cranial
Occulomotor & trochlear Ns.
nerves :
are attached to midbrain.
Trigeminal N. is attached to
antero-lateral surface of pons.
Abducent, Facial & vestibulocochlear Ns. are lying between
pons & M.O. from medial to lateral.
The base of the brain
showing locations of cranial
nerves
Hypoglossal N. lies between
olive & pyramid in the M.O. / but
glossopharyngeal, vagus &
accessory Ns. are attached to
postero-lateral sulcus of M.O.,
lateral to olive.
Afferent Nerve Nuclei :
Large Trigeminal Sensory
nucleus, extends the whole length of
brain stem and cervical spinal
cord. receiving general sensation
from the head via trigeminal N.
Vestibular & Cochlear nuclei that
are located in upper M.O., receiving
hearing & positional sense via
vestibulo-cochlear N.
Dorsal aspect of brain stem showing locations
of Afferent cranial N. nuclei (left) , and Efferent
cranial N.nuclei (right) , in which the same
colours have a common embryological origin.
Nucleus solitarius located in
upper M.O., receiving taste
sensation via facial &
glossopharyngeal Ns.
Efferent Nerve Nuclei :
Somatic efferent column : supplies
striated Ms. in head, including :
1- Oculomotor nucleus.2-Trochlear nucleus.
3-Abducent nucleus. 4-Hypoglssal nucleus.
Branchiomotor (special visceral)
efferent column : supplies striated Ms. derived
from branchial arches, including :
1- Trigeminal motor nucleus.
2- Facial motor nucleus.
3- Nucleus ambiguus.
Parasympathetic (general visceral)
efferent column : supplies glands & smooth
Ms. of viscera , including :
1- Edinger- Westphal nucleus.
2- Sup.& Inf. Salivary nuclei.
3- Dorsal nucleus of vagus.
Somatic efferent Nerve Nuclei
Oculomotor nucleus : lies at the
base of periaqueductal grey of
midbrain at the level of superior
colliculus. Its efferent Fs. run in
oculomotor N. to innervate levator
palpebrae superiooris + all
extraocular Ms. Except L.R & S.O
 Trochlear nucleus : lies at the
ventral part of periaqueductal grey of
midbrain at the level of inferior
colliculus. Its efferent Fs. run in
trochlear N. to innervate S.O.muscle.
Somatic efferent Nerve Nuclei :
Abducent nucleus : lies in the
caudal pons , beneath floor of
4th vent. Its efferent Fs. run in
abducent N. to supply L.R.
Hypoglossal nucleus : lies in
the rostral M.O. its efferent Fs.
run in hypoglossal N. to supply
all Ms. of tongue Except
palatoglossus muscle.
Branchiomotor efferent Nerve Nuclei
Trigeminal motor nucleus : lies
in the tegmentum of the mid-pons and its motor
Fs. run in mandibular branch of trigeminal N.
to supply structures of 1st pharyngeal arch as
Ms. of mustication, mylohyoid, ant.belly of
digastric, tensor tympani (middle ear) & tensor
veli palatini.(soft palate).
Facial motor nucleus : lies in the
caudal pontine tegmentum, its motor Fs. run in
facial N. to innervate Ms. of facial expression,
stapedius muscle (middle ear) & other Ms.
derived from 2nd pharygeal arch (stylohyoid,
post.belly of digastric).
Nucleus ambiguus : it is a long nucleus
lies in M.O., sending motor Fs. in 9th ,10th &
cranial root of 11th nerves to innervate Ms. of
pharynx & larynx derived from 3,4& 6
Parasympathetic efferent Nerve
Nuclei :
Edinger-Westphal nucleus
lies in midbrain adjacent to oculomotor
nucleus. It is the parasymp. part of
oculomotor nucleus. It gives preganglionic
parasymp. motor Fs. Via oculomotor N. into
ciliary ganglion, which sends postganglionic
Fs. to innervate sphincter pupillae & ciliary
Ms. in the eye.
Superior salivary nucleus :
lies in caudal pontine tegmentum, it gives
preganglionic Fs. Via facial N. into pterygopalatine & submandibular ganglia , which
gives postganglionic Fs. to innervate lacrimal
gl., Nasal and oral M.Ms. & submandibular
and sublingual salivary glands…. respictevly
Parasympathetic efferent Nerve
Nuclei :
Inferior salivary nucleus :
lies in pontine tegmentum, sends preganglionic Fs. Via glosso-pharyngeal
N. into otic ganglion , which sends
post-ganglionic Fs. to parotid gland.
+ via Vagus N. to supply mucous
gland of G.I.T & respiratory glands.
Dorsal motor nucleus of
vagus : lies in the rostral M.O.
lateral to hypoglossal nucleus, it gives
preganglionic parasymp.Fs. Via
vagus N. to supply ms. of abdominal
& respiratory viscera.
Cranial Nerves : III : Oculomotor N.
This N. contains 2-types of fibres : 1- Somatic motor efferent Fs.
from oculomotor nucleus to all extrinsic eye Ms. Except S.O &L.R.
2- Preganglionic parasymp. motor Fs. from Edinger-Westphal
nucleus into ciliary ganglion which sends postganglionic Fs. via
short ciliary nerves into constrictor pupillae & ciliary ms.
T.S of midbrain at the level of sup.colliculus
to illustrate the pathway of pupillary light reflex.
During the visual pathway ,small
Fs. leave the optic tract to synape in
pretectal nucleus, which projects
bilaterally Fs. to Edinger-Westphal
nuclei of occulomotor ,that send
efferent parasympathetic Fs. Via
oculomotor nerves on both sides to
sphincter pupillae ms.
Note that pretectal area involves in
mediation of pupillary light reflex.
Accomodation Reflex :
Fixation upon a nearby object,
involves contraction of ciliary
muscles to increase the convexity
of lens, thus focusing the image.
It is also accompanied by
activation of sphincter pupillae m.
Fibres from visual frontal cortex
activate the parasymp. EdingerWestphal nuclei on both sides to
supply ciliary & sphincter pupillae
Ms.
Optic pathway and Visual reflexes
(pupillary light R.+ accomodation R.)
IV : Trochlear Nerve :
This N. carries only somatic
motor efferent Fs. from the trochlear
nucleus in midbrain (level of inferior
colliculus) to supply the S.O. of
opposite side.
Trchlear N. ,the only nerve
emerges from the post.surface of
brain - stem ,then appears on the
ventral aspect of the midbrain.
T.S of midbrain at the level of
inferior colliculus ,showing the
location of trochlear nucleus (at the
base of periaquaductal grey matter) and
course of trochlear N.Fs.
VI : Abducens Nerve :
Contains only somatic motor
neurones in the abducens nucleus
,which located in caudal pons
beneath the floor of 4th ventricle.
Fibres emerge from the ventral
surface of brain stem at the junction
between the pons & pyramid of
M.O
 The nerve then passes in the
cavernous sinus and enter orbit
through sup. orbital fissure to supply
L.R muscle to abduct the eyeball.
Lesions of cranial nerves III,IV and VI :
Oculomotor N. palsy by a lesion
of occulomotor nucleus in midbrain or
compression by aneurysm or tumour
leads to ptosis , dilatation of pupil that
is unresponsive to light &
accommodation reflexes and inability to
move eyeball upwards, downwards and
inwards (adduction).
Abducens N. palsy leads to
inability to move the eyeball outwards
(abduction).
Note right ptosis .
Combined unilateral palsies of III,
Note with elevation of right eyelid, the eyeball IV,and VI during their course in
can be seen abducted and the pupil dilated.
cavernous sinus , sup. Orbital fissure or
Note failure of left eyeball abduction due to within the orbit , lead to:
lesion of left abducent N.
1-ptosis.
2-dilatation of pupil.
3-paralysis of all eye movements
V : Trigeminal Nerve :
It is the largest cranial N., it
has both sensory Fs. that are
distributed via ophthalmic,
maxillary and mandibular to the
head --- & motor Fs. Via
mandibular N. to ms. of
mastications (Ms.of 1st arch).
Superficial distribution of sensory fibres of the 3
divisions of trigeminal nerve.
It attaches to the ventrolateral
aspect of pons by 2 roots
(a large sensory laterally & a
smaller motor medially).
V : Sensory components
of Trigeminal Nerve :
Trigeminal sensory nucleus
Brain stem and location of trigeminal
sensory nucleus & its major connections.
consists of 3-subnuclei :
1-Chief (principle) sensory nucleus
lies in pontine tegmentum (midpon), it recevies touch sensation.
2-Spinal nucleus extends caudally
through the medulla and upper
cervical spinal cord to become
continuous with substantia
gelatinosa, it recevies pain &
temp.sensation from face & scalp.
3-Mesencephalic nucleus in
midbrain, it recevies proprioception
(deep) sensation from head.
Sensory components of Trigeminal nerve
(for touch/pressure & pain/temperature) :
Afferent Fs. of touch, pressure, pain
& temperature are recevied from skin
of face ,scalp, via peripheral
processes
(ophthalmic,maxillary+sensory part
of mandibular)… whose cell bodies
(first neurones) are situated in
trigeminal ganglion (located at the
convergence of ophthalmic , maxillary and
mandibular nerves).
Brain stem and location of trigeminal
sensory nucleus & its major connections.
Afferent Fs.(centeral axons)
conveying touch terminate in principal
nucleus, and those carrying pain &
temp. end in nucleus of spinal tract
of trigeminal.
Sensory components of Trigeminal nerve
(for proprioceptive sensation):
1st neurone for Proprioceptive :
peripheral afferents (via mandibular nerve)
from Ms.of mustication & temporomandibular joint have their cell bodies not in
trigeminal ganglion but in mesencephalic
nucleus of trigeminal ( the only primary
afferents to have cell bodies within C.N.S).
The centeral axons of the cells of
mesencephalic nucleus descend medially to
synapse around Motor Nucleus of Trigeminal
(2ND neurone) in pons.
Brain stem and location of trigeminal
sensory nucleus & its major connections.
Axons arising from 2nd neurones in
trigeminal nuclei decussate to form
contralateral trigemino-thalamic tract, which
terminates in contralateral (VP) nucleus of
thalamus that sends Fs. to sensory cortex.
Motor components of
Trigeminal Nerve :
The motor Fs.of trigeminal N.
arise from the trigeminal motor
nucleus , which lies in pontine
tegmentum.
T.S of pons at the level of
Trigeminal nuclei.
The axons leave the pons to
join the mandibular division of
trigeminal , to innervate
1st pharyngeal arch drevatives :
1- 4 Ms. of mastication.
2- 4 other Ms. : mylohyoid,
anterior belly of digastric, tensor
palati (soft palate) & tensor
tympani (middle ear).
Lesions of Trigeminal Nerve :


Herpes Zoster infection of sensory root of trigeminal N.
….. Leads to severe stabbing pain & eruption of vesicles
localised to skin supplied by its branches : ophthalmic ,
or maxillary or mandibular N….. Trigeminal Neuralgia.
Syringo-bulbia ,it is a disease of unknown etiology which
affects the closed M.O, causes central cavitation of
medulla caudal to 4th V. , leading to destruction &
damage of decussating trigemino-thalamic Fs., causing
selective loss of pain & temp. sensation in the face
( dissociated sensory loss), mostly leading to destruction
of the cervical spinal cord (syringomyelia) =cavitation of
spinal cord.
1. All of the following are corresponding to parasympathetic
efferent nuclei EXCEPT:
a.Superior salivary nucleus.
b.Inferior salivary nucleus.
c.Abducent nucleus.
d.Edinger-Westphal nucleus.
e.Dorsal motor nucleus of vagus.
2. Which of the following is Corresponding to branchiomotor
efferent nuclei ?
a.Edinger-Westphal nucleus.
b.Dorsal motor nucleus of vagus.
c.Oculomotor nucleus.
d.Nucleus ambiguus.
e.Hypoglossal nucleus.
3.Bulbar palsy is confirmed by degeneration of one of the following
Nuclei :
a.Oculomotor nucleus.
b.Mesencephalic nucleus.
c.Abducent nucleus.
d.Trochlear nucleus.
e.Nucleus ambiguus.
4.Syringobulbia leads to destruction of :
a.The lateral lemniscus.
b.The trigeminal lemniscus.
c.The corticobulbar tract.
d.The spinothalamic tract.
e.The trapezoid body.
VII : Facial Nerve :
It consists of 2 roots :
1-The lateral root (Nervous intermedius) contains sensory &
parasymp.Fs.
2- The medial root is the motor root.
VII : Facial Nerve :
It carries 3-types of fibres : 1- Efferent motor (branchiomotor) Fs.
From facial motor nucleus in pons to : Ms. of 2nd arch , Ms. of facial expression &
stapedius. 2-Efferent parasympathetic secretomotor Fs. Carried by
lateral root of facial nerve (nervus intermedius) From sup. salivary nucleus in pons
: to pterygopalatine & submandibular ganglia to lacrimal gland , palate, nasal &
oral m.m, /and submandibular & sublingual salivary glands.
3- Sensory Taste Fs. from anterior 2/3 of tongue, cell bodies in sensory
geniculate ganglion in middle ear , and run in nervus intermedius to end in
Nucleus Solitarius in M.O. projecting into (v.p) of thalamus then to sensory cortex
VII : Facial Motor Nerve :
Motor Fs. of facial nucleus in pons , via facial N. looping over
abducens nucleus , then leaving the brain stem to supply : Ms.of
facial expression ,platysma ,stylohyoid , post.belly of digastric &
stapedius of middle ear.
Facial motor nucleus receives other afferents from brain stem for
mediation of certain reflexes and from cerebral cortex for
cortico-bulbar pyramidal tract.
VII : Facial Motor Nerve :
Reflex connections mediate 1- protective eye closure in response to sudden strong
stimuli via facial N. to supply orbicularis oculi to close & protect the eye.
2- corneal reflex through Fs. from trigeminal sensory nucleus, to motor nucleus of facial,
then via facial N. to orbicularis oculi in response to tactile stimulation of cornea.
Afferents from cortical motor areas (cotico-bulbar Fs.) supply Ms. of upper face
which are distributed bilaterally (from Rt.& left C.hemispheres) , but those supplying
Ms. of lower face are crossed. So, Unilateral upper motor neurone lesion (UMNL)
leads to lower facial Ms. paralysis of opposite side only, but upper Ms. are intact.
Bell’s Palsy :LMN facial paralysis



It is due to acute unilateral inflammation of facial
nerve within the skull (in facial canal).
Manifested by paralysis of facial muscles of upper &
lower parts of face on the same side of lesion..
Manifested by pain around ear , - failure to close eye,
absent corneal reflex, - loss of taste sensation in
anterior 2/3 of tongue, & hyperacusis =increased
sound perception due to paralysis of stapedius.
(action of stapedius = damping down the intensity of high
pitched sounds by damping down movement of stapes)

If herpes zoster virus is the inflammatory agent ,
a vesicular rash appear in ext. auditory canal & m.m
of oropharynx (Ramsay Hunt syndrome).
VIII : Vestibulocochlear Nerve :
It is purely sensory nerve.
It has 2-components ,
1- Vestibular N., which carries
balance sensation from utricle,
sacule & semicircular canals.
2- Cochlear N., which carries
hearing sensation.
It emerges from ponto-medullary
junction at cerebello-pontine angle
VIII : Vestibular Nerve :
Cells of origin :
vestibular ganglion ,lying in
internal acoustic meatus.
The peripheral process :
carries sensation from
utricle,saccule & semicircular
canals (membranous labyrinth).
Central process : leaves
vestibular ganglion and joins
cochlear N.
Distribution of Vestibular Nerve
It enters the brain in groove
between pons & M.O. to end in
the Vestibular nuclei in M.O.
Vestibular Nerve Fibres :
1-Efferent Fs. From the 4
vestibular nuclei to cerebellum
( flocculo-nodular lobe) through inferior
cerebellar peduncle to control balance.
2-Efferent Fs. descend uncrossed
to spinal cord from lateral vestibular
(Deiter’s)nucleus to form vestibulo-spinal
tract , assist to maintain balance by
influencing muscle tone of body.
3-Efferent Fs. to ocular nuclei of
Vestibular nerve nuclei & their central
connections (rostral M.O.)
oculomotor , trochlear & abducent
through medial longitudinal fasciculus ,
for coordination of head & eye
movements.
Vestibular Nerve Fibres :
4-Efferent Fs. ascend from
vestibular nuclei to relay in (VP)
nucleus of thalamus to reach
the cerebral cortex , at the
vestibular area of sensory cortex
which adjacent to primary
sensory cortex in parietal lobe at
inferior parietal lobule just above
lateral fissure.
Vestibular nerve nuclei & their
central connections
Lateral aspect of cerebral hemisphere
location of vestibular area in cerebral cortex : adjacent to primary
sensory cortex in inferior parietal lobe/ or above lateral fissure, adjacent to
auditory cortex in temporal lobe.
Cochlear Nerve :
1st order neurones : it is formed
by the cells of spiral ganglion.
Peripheral Fs. conduct sound
from the organ of Corti in the
cochlea.
The axons of these cells
bifurcate to end in dorsal &
venteral cochlear nuclei , which
lie close to inf.cerebellar
peduncle.
Ascending connections of auditory
component of vestibulo-cochlear nerve.
2nd order neurones : it is
formed of cells of cochlear nuclei.
Most axons of these cells Cross to
opposite side of pons as trapezoid
body.
At trapezoid body, some Fs.may
terminate in superior olivary nucleus.
Most Fs. Ascend from sup.olivary
nuclei to form the lateral lemniscus
then ascend to end in inferior
colliculus of midbrain.
The inferior colliculus sends axons
to medial geniculate nucleus of
thalamus.
Ascending connections of auditory
component of vestibulo-cochlear nerve.
3rd order neurone : axons
arise from MGN pass through
internal capsule to primary
auditory cortex, which is
located in Heschl’s gyri lying
in superior temporal gyrus and
hidden within the lateral fissure
Auditory association cortex
( Wernick’s area) is an area of
temporal lobe surrounding the
primary auditory cortex , in
which the auditory information
is interpreted ( for knowing the
meaning of sounds).
Ascending connections of auditory
component of vestibulo-cochlear nerve.
Lateral aspect of cerebral hemisphere
Note primary auditory cortex & Wernicke’s area in
superior temporal gyrus.
Acoustic Neuroma :
It is a benign tumour of vestibulocochlear
nerve in cerebello-pontine angle.
 So, there is attacks of dizziness, deafness &
ataxia (disturbances of voluntary movement).

IX : Glossopharyngeal Nerve Fibres :
It is a mixed N. ,attached lateral to
olive in rostral medulla and leaves the
skull through jugular foramen.
It contains :
1-Afferent Sensory Fs. for Taste
sensation from post.1/3 of
tongue+ general sensation from
phartnx end in trigeminal sensory
nucleus.
2-Afferent visceral (chemo-&
baroreceptors in carotid body+
sinus)& taste Fs. : end in Nucleus
Glossopharyngeal nerve nuclei &
their central connections. Red= motor,
brown= parasymp., blue = sensory
Solitarius of medulla.
IX : Glossopharyngeal Nerve Fibres :
3-Efferent motor Fibres :
arises from its main motor nucleus
in the rostral part of nucleus
ambiguus of medulla to supply
stylopharyngeus involved in
swallowing.
4-Efferent Parasympathetic
Fibres : arises from inferior salivary
nucleus of rostral medulla to synapse
in otic ganglion, then via postganglionic Fs.innervate parotid gland.
Glossopharyngeal nerve nuclei &
their central connections. Red= motor,
brown=parasymp.,blue=sensory
X : Vagus Nerve :
Vagus nerve Nuclei & their
central connections.
It is mixed nerve, attached
lateral to olive of medulla caudal
to glosso-pharyngeal N. in groove
between olive & inf. cerebellar
peduncle.
It recevies afferent Fs.from :
1-Receptors for general sensation
in pharynx, larynx, tympanic
membrane, ext.acoustic meatus.
2- Chemoreceptors in aortic
bodies and baroreceptors in
aortic arch.
3- Visceral receptors in thoracic
& abdominal viscera.
X : Vagus Nerve Fibres :
1-Afferent Fs.for general
sensation : end in sensory nucleus
of trigeminl and - visceral sensory
afferents end in nucleus solitarius.
2-Efferent Motor Fs. : arise from
nucleus ambiguus of medulla
(main motor nucleus of vagus) to
innervate Ms. of soft palate,
pharynx, larynx to control
swallowing and speech.
Vagus nerve Nuclei & their central
connections.
3-Efferent Parasymp. Fs. : arise
from dorsal motor nucleus of
vagus to supply CVS, RS, & GITS.
XI :Accessory Nerve :
It is purely motor , consists of
cranial part & spinal part.
The cranial part emerges from
lateral aspect of medulla below vagus
N. It arises from caudal part of
nucleus ambiguus of medulla.
-At the level of jugular foramen it
joins vagusN. to supply Ms. of soft
palate, pharynx & larynx.
Spinal root of accessory arises
from upper 5 cervical spinal cord
segments. It ascends to the side of
Diagram of caudal medulla & rostral spinal
medulla to join the cranial root till
cord to illustrate origin and course of vagus
the jugular F., it separates to supply
& accessory nerves.
sternomastoid & trapezius Ms.
XII : Hypoglossal Nerve :
It is purely motor , supplying all
extrinsic & intrinsic Ms. of tongue
except palatoglossus (by pharyngeal
plexus).
It arises from hypoglossal nucleus in
medulla ( beneath floor of 4th V.).
It emerges from M.O. between olive
& pyramid.
T.S.of medulla to illustrate origin
& course of hypoglossal nerve.
Motor neurone disease and lesions of
cranial nerves IX-XII :



Occures in those over 50 years due to chronic degeneration
of cortico-bulbar tracts projecting to nucleus ambiguus
(sends motor Fs.in 9,10,11 nerves) & hypoglossal nucleus ,
leading to dysphonia (difficulty in phonation), dysphagia
(difficulty in swallowing) , dysarthria ( difficulty in
articulation) and weakness & spasticity of tongue
(pseudobulbar palsy).
There is also degeneration of nucleus ambiguus &
hypoglossal nucleus themselves, leading to
dysphonia,dysphagia, dysarthria and weakness, wasting &
fasciculation of tongue (bulbar palsy).
IX-XII nerves can be damaged by tumours in skull
foramina, lead to dysphonia, dysphagia, + wasting of
sternomastoid & trapezius Ms. + Weakness & wasting of
tongue.