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College of Medicine – ‫كلية الطب‬
Cranial Nerves
Dr.Munirha Batarfi
MD, MSc & PhD
College of Medicine – ‫كلية الطب‬
Cranial Nerves
- Olfactory (I)
- Optic (II)
- Oculomotor (III)
- Trochlear (IV)
- Trigeminal (V)
- Abducens (VI)
- Facial (VII)
- Vestibulocochlear (VIII)
- Glossopharyngeal (IX)
- Vagus (X)
- Accessory (XI)
- spinal accessory(XII)
- Hypoglossal (XII)
2
Cranial Nerves
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There are 12, paired cranial nerves.
The first 2 cranial Ns. attach directly to forebrain (frontal lobe) , while the
rest attach to brain stem.
1- Olfactory system is attached to forebrain
2- Optic N. also is discribed in visual pathway.
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.
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Cranial Nerves
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3 & 4- Occulomotor & trochlear Ns. are attached to midbrain.
5- Trigeminal N. is attached to antero-lateral surface of pons.
6 , 7 & 8- Abducent, Facial & vestibulo-cochlear Ns. are lying between pons
& medulla oblongata from medial to lateral.
9- Hypoglossal N. is attached to antero-lateral sulcus of medulla oblongata.
10, 11, & 12- Glossopharyngeal, vagus & accessory Ns. are attached to
postero-lateral sulcus of medulla oblongata
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Cranial Nerves
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College of Medicine – ‫كلية الطب‬
Abducens (VI)
General characteristics of CN VI
● a pure GSE nerve that innervates the lateral rectus, which abducts the
eye.
● arises from the abducent nucleus of the caudal pons.
● exits the brainstem from the inferior pontine sulcus.
● passes through the cavernous sinus to enter the orbit via the superior orbital
fissure.
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Abducens (VI)
B. Clinical correlations: CN VI paralysis
● results in the following conditions:
1. Convergent strabismus (esotropia), with inability to abduct the eye
because of the unopposed action of the medial rectus.
2. Horizontal diplopia, with maximum separation of the double images
when looking toward the paretic lateral rectus.
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ABDUCENT NERVE
7th n.
P
petrous temporal bone
Pons
V
abducent n.
1
P
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College of Medicine – ‫كلية الطب‬
Facial (VII)
General characteristics of CN VII
● mediates facial movements, taste, salivation, and lacrimation.
● the nerve of the second pharyngeal arch.
● includes the facial nerve proper (motor division), which contains the
SVE fibers that innervate the muscles of facial expression.
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● includes the intermediate nerve (sensory division),
All first-order sensory neurons are found in the geniculate ganglion
within the temporal bone.
● enters the internal auditory meatus and the facial canal.
● exits the facial canal and skull via the stylomastoid foramen.
13
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Facial (VII)
1.
● has cell bodies in the geniculate ganglion.
● innervates the posterior surface of the external ear via the posterior
auricular branch of the facial nerve.
● projects centrally to the spinal trigeminal tract and nucleus.
2.
● has cell bodies in the geniculate ganglion.
● projects centrally to the solitary tract and nucleus.
● innervates the taste buds from the anterior two-thirds of the tongue via:
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3. Chorda tympani
● located in the tympanic cavity medial to the tympanic membrane and lateral
to the malleus.
● contains SVA and general visceral afferent (GVA) fibers.
● joins the lingual nerve (a branch of CN V)
4.
● a parasympathetic component that innervates the lacrimal, submandibular,
and sublingual glands.
● contains preganglionic neurons in the superior salivatory nucleus of the
caudal pons.
15
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Facial (VII)
Lacrimal pathway
● begins in the superior salivatory nucleus, which projects via the intermediate
nerve, the greater petrosal nerve, and the nerve of the pterygoid canal to the
pterygopalatine ganglion.
● continues as the postganglionic neurons of the pterygopalatine ganglion
project through the inferior orbital fissure and via the zygomatic nerve (a
branch of CN V) and the
lacrimal nerve (a branch of CN V) to innervate the lacrimal gland.
.
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Submandibular pathway
● begins in the superior salivatory nucleus, which projects via the intermediate
nerve and chorda tympani to the submandibular ganglion.
5.
● arises from the facial motor nucleus of the caudal pons and exits the
brainstem in the CP angle.
● enters the internal auditory meatus, traverses the facial canal, sends a branch
to the stapedius, and exits the skull via the stylomastoid foramen.
● innervates the muscles of facial expression, the stylohyoid, the posterior
belly of the digastric, and stapedius
17
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College of Medicine – ‫كلية الطب‬
Facial (VII)
Clinical correlations: lesions of CN VII
● result in the following conditions:
1. Flaccid paralysis of the muscles of facial expression (upper and lower
face)
2. Loss of the corneal (blink) reflex (efferent limb), which may lead to
corneal ulceration (keratitis paralytica)
3. Loss of taste (ageusia) from the anterior two-thirds of the tongue
4. Hyperacusis (increased acuity to sounds), due to stapedius paralysis
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Facial (VII)
5. Bell’s palsy
● caused by trauma to the nerve within the facial canal.
● a lower motor neuron (LMN) lesion with paralysis of all muscles of
facial expression.
Bell phenomenon
● normally seen in about 75% of population.
occurs when trying to close the eyes—the affected eye looks up and out.
● observable because of failure of orbicularis oculi to close eyelids.
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College of Medicine – ‫كلية الطب‬
College of Medicine – ‫كلية الطب‬
College of Medicine – ‫كلية الطب‬
VII : Facial Nerve
This nerve 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-Afferent Taste sensory Fs. From anterior 2/3 of tounge. These Fs. are processes
of cells in sensory geniculate ganglion in middle ear , and run in nervus
intermedius and end in nucleus solitarius, lying in M.O.
3-Efferent preganglionic parasympathetic secretomotor Fs. Carried by sensory
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.
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VII : Facial Nerve :
The lateral root contains sensory & parasymp.Fs. is called nervus
intermedius , but the medial root is the motor root.
The sensory Fs. ends in nucleus solitarius in medulla and then Fs.
project to V.P.nucleus of thalamus, which sends Fs. to sensory cortex of
parietal lobe.
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VII : Facial Nerve :
Motor Fs. of facial nucleus in pons , 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 area of brain stem for
mediation of certain reflexes and also from cerebral cortex , (cortico-bulbar
pyramidal tract).
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VII : Facial Nerve :
Reflex connections mediate
1- protective eye closure in response to sudden strong visual stimuli through Fs.
from sup. Colliculus (tectum of midbrain), 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. in response to
tactile stimulation of cornea.
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!
Afferents from cortical motor areas (cotico-bulbar Fs.) supply Ms. of
upper face (frontalis & orbicularis oculi) are distributed bilaterally , 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.
28
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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 (unilaterally) on the same side of lesion..
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.
FACIAL NERVE
1
facial n.
A
geniculate g.
2
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3
B
4
temporal
C
tympanic cavity
1
2
a
facial n.
zygomatic
3
buccal
5
mandibular
D
E
F
6
cervical
Intra cranial origin
-motor nucleus in the pons (1)
-Superior salivary nucleus (2)
-Nucleus solitarius (3)
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Glossopharyngeal (IX)
General characteristics of CN IX
● mediates taste (gustation), salivation, and (with CN X and CN XII)
swallowing
mediates input from the carotid sinus, which contains baroreceptors that
monitor arterial blood pressure.
● mediates input from the carotid body, which contains chemoreceptors
that monitor the carbon dioxide and oxygen concentration of the blood.
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Glossopharyngeal (IX)
General characteristics of CN IX
● the nerve of the third pharyngeal arch.
● predominantly a sensory nerve.
● exits the brainstem (medulla) from the postolivary sulcus with CN X.
● exits the skull via the jugular foramen with CN X and CN XI.
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Glossopharyngeal (IX)
1.
● innervates the middle ear cavity and part of the external auditory meatus.
● has cell bodies in the superior glossopharyngeal ganglion.
● projects its central processes to the spinal trigeminal tract and nuc
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Glossopharyngeal (IX)
2.
● innervates structures derived from endoderm (e.g., foregut).
● innervates the mucous membranes of the posterior third of the tongue, tonsil,
upper pharynx (soft palate), tympanic cavity, and auditory tube.
● innervates the carotid sinus (baroreceptors) and the carotid body
(chemoreceptors).
● has cell bodies in the inferior (petrosal) ganglion.
● the afferent limb of the gag reflex and the carotid sinus reflex.
3.
● innervates the taste buds of the posterior third of the tongue.
● has cell bodies in the inferior (petrosal) ganglion.
● projects its central processes to the solitary tract and nucleus.
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Glossopharyngeal (IX)
4.
● innervates the stylopharyngeus.
● arises from the nucleus ambiguus of the lateral medulla.
5.
● a parasympathetic component that innervates the parotid gland.
● consists of preganglionic neurons in the inferior salivatory
nucleus of the medulla that project, via the tympanic nerve and
the lesser petrosal nerve to the otic ganglion;
postganglionic fibers from the otic ganglion project to the parotid
gland via the auriculotemporal nerve (CN V3)
GLOSSO-PHARYNGEAL NERVE (9TH CRANIAL NERVE )
inf. cerebellar peduncle
Nuclei:
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-Nucleus ambiguus (A)
1
-Nucleus dorsalis (B)
-Nucleus solitarius (C)
-Inferior salivary nucleus (D)
pons
the n. in groove between olive and inf. cerebellar peduncle
2
1
medulla
4
3
6
2 ganglia
olive
glosso- pharyngeal n.
tongue
8
5
9
Course of glosso-pharyngeal nerve (9th cranial nerve)
7
site of hyoglossus m.
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BRANCHES OF GLOSSOPHARYNREAL NERVE
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1.Tympanic nerve:
2. Nerve to
stylopharyngeus.
3.Pharyngeal
branches.
4.Carotid nerve .
c
d
f
b
ganglia1
e
a
6
glossopharyngeal n.
tongue
2
5.Terminal
branches.
5
4
3
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Glossopharyngeal (IX)
Clinical correlations: lesions of CN IX
1. Loss of the gag (pharyngeal) reflex (interruption of
afferent limb)
2. Loss of the carotid sinus reflex (interruption of the sinus
nerve)
3. Loss of taste from the posterior third of the tongue
4. Glossopharyngeal neuralgia
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Vagus (X)
General characteristics of CN X
● mediates phonation, swallowing (with CN IX and CN XII),
elevation of the palate, and taste.
● innervates viscera of the neck, thorax, and abdomen.
● the nerve of the fourth and sixth branchial arches.
● exits the brainstem (medulla) from the postolivary sulcus.
● exits the skull via the jugular foramen with CN IX and CN XI.
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Vagus (X)
1.
● innervates the infratentorial dura (with C2 and C3) external ear, external
auditory meatus, and tympanic membrane
● has cell bodies in the superior (jugular) ganglion.
● projects its central processes to the spinal trigeminal tract and nucleus.
2.
● innervates the mucous membranes of the pharynx, larynx, esophagus,
trachea, and thoracic and abdominal viscera (to the mid-transverse colon).
● has cell bodies in the inferior (nodose) ganglion.
● projects its central processes to the solitary tract and nucleus.
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Vagus (X)
3.
● innervates the taste buds over the epiglottis and soft palate.
● has cell bodies in the inferior (nodose) ganglion.
● projects its central processes to the solitary tract and nucleus.
4.
● innervates the pharyngeal arch muscles of the larynx and pharynx, striated
muscle of the upper esophagus, musculus uvalae, and levator palati and
palatoglossus.
● arises from the nucleus ambiguus in the lateral medulla.
● provides the efferent limb of the gag reflex.
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Vagus (X)
5.
● innervates the viscera of the neck and the thoracic and abdominal
cavities as far as the mid-transverse colon.
● consists of preganglionic parasympathetic neurons in the dorsal motor
nucleus of the vagus, which project to the intramural ganglia of the viscera.
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Vagus (X)
Clinical correlations: lesions of CN X
● result in the following conditions:
1. Ipsilateral paralysis of the soft palate, pharynx, and larynx leading to
dysphonia (hoarseness), dyspnea, dysarthria, and dysphagia
2. Loss of the gag (palatal) reflex (efferent limb)
3. Anesthesia of the pharynx and larynx, leading to unilateral loss of the
cough reflex
4. Aortic aneurysms and tumors of the neck and thorax
● frequently compress the vagal nerve.
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X : Vagus Nerve
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It is mixed nerve, attached lateral to olive of medulla caudal to glossopharyngeal 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-Receptors in thoracic & abdominal viscera.
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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.
3-Efferent Parasymp. Fs. : arise from dorsal nucleus of vagus to
supply CVS,RS,& GITS.
VAGUS NERVE
vagus
1
3
Nuclei : 4 nuclei in the medulla
-Nucleus ambiguus (A)
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-Nucleus dorsalis (B)
pharyngeal br.
-Nucleus solitarius (C)
-Spinal tract and nucleus of
trigeminal nerve (D)
carotid br.
sup. laryngeal
C
B
2
Inf. cerebellar peduncle
recurrent laryngeal
A
medulla
vagus n.
4
olive
pyramid
D
5
COURSE OF VAGUS n.
BRANCHES OF VAGUS NERVE
vagus n.
1. Meningeal branch.
2. Communicating branches.
3. Auricular branch.
1
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4. Pharyngeal branch.
3
5 .Superior laryngeal nerve which
divides into:
a.External laryngeal nerve
4
(motor)
b.Internal laryngeal nerve
(sensory)
5
6. Carotid branch
7. Cardiac branches.
8. Right recurrent laryngeal nerve.
R.L.N
R.L.N
6
7
8
S
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Accessory (XI)
(spinal accessory)
General characteristics of CN XI
● not actually a cranial nerve, as it originates in the spinal cord.
● mediates head and shoulder movement.
● arises from the anterior horn of cervical segments C1 to C6.
● spinal roots exit the spinal cord laterally between the anterior and posterior
roots, ascend through the foramen magnum, and exit the skull via the
jugular foramen.
● innervates the sternocleidomastoid (with C2) and trapezius (with C3 and
C4).
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B. Clinical correlations: lesions of CN XI
● result in the following conditions:
1. Paralysis of the sternocleidomastoid muscle
● results in difficulty in turning the head to the side opposite the lesion.
2. Paralysis of the trapezius muscle
● results in a shoulder droop.
● results in the inability to shrug the ipsilateral shoulder.
51
ACCESSORY NERVE
medulla
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the cranial root joins
the vagus
foramen
magnum
7
6
ACCESSORY NERVE
CRANIAL PART
SPINAL PART
trapezius
10
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Hypoglossal (XII)
General characteristics of CN XII
● mediates tongue movement.
● arises from the hypoglossal motor nucleus of the medulla.
● exits the medulla in the preolivary sulcus.
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Hypoglossal (XII)
exits the skull via the hypoglossal canal.
● innervates intrinsic and extrinsic muscles of the tongue.
B. Clinical correlations: CN XII
● When it is transected, hemiparalysis of the tongue results.
● The tongue points toward the weak side due to the unopposed
action of the opposite genioglossus upon protrusion.
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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.
It also receives coticobulbar Fs. from contralateral motor cortex
to supply Ms. of tongue for speech.
HYPOGLOSSAL NERVE
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Nucleus:
Hypoglossal nerve nucleus (A)
9
COURSE OF HYPOGLOSSAL NERVE
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BRANCHES OF HYPOGLOSSAL NERVE
The first cervical (C1) gives a
contribution to the hypoglossal
nerve which gives the branches
of hypoglossal nerve.
hypoglossal n.
4genio- glossaus
hypoglossal canal
tongue
medulla
1. Descendens hypoglossi (1)
hyoglossus m.
3
2. Nerve to thyrohyoid (2)
3. Nerve to geniohyoid (3)
2
1
4. The pure hypoglossal
nerve fibers supply the
intrinsic
and extrinsic muscles of
tongue (4) (except the
palatoglossus).
descendens cervicalis
descendens hypoglossi
ansa cervicalis
thyrohyoid m.
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References
• Clinical Neuroanatomy for Medical Students, Richard S. Snell-6th
Edition.
• Clinical Neuroanatomy and related neuroscience. M.J.T. FitzGerald,
Jean Folan-Curran, Fourth Edition.
• Crossman, AR and Neary D, Neuroanatomy: An Illustrated Colour
Text.
• Haines, DE, Neuroanatomy: An Atlas of Structures, Sections and
Systems.
• Agur, A. M. R. and A. F. Dalley. 2009. Grant’s Atlas of Anatomy, 12th
Edition. Lippincott, Williams & Wilkins, New York.
• Moore, K. L., A. F. Dalley and A. M. E. Agur. 2010. Clinically
Oriented
Anatomy, 6th Edition. Lippincott, Williams & Wilkins,
New York.
• Sadler, T. W. 2004. Langman’s Medical Embryology, 9th Edition.
Lippincott, Williams & Wilkins, New York.