1. Cranial nerves
pathways
I-XII
BY
Prof. Dr. Abdul Waheed Ansari
Chairperson & Prof. Anatomy,
RAKCODS/RAKCOMS.
1/7/2014
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2. There are 12 pairs of cranial nerves
• Purely sensory cranial nerves are :Olfactory/Optic and Auditory.
• Purely motor cranial nerves
are:Occulomotor/Trochlear/Abducent
/Hypoglossal
• Mixed cranial nerves are:- Trigeminal/
Facial/Glossopharyngeal/Vagus.
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4. I – Olfactory nerve
• It arises from the neuroepithelium of nasal cavity.
• 18/20 Fila olfactoria pass through the cribriform plate
of ethmoid and enters the anterior cranial fossa.
• It synapses with the olfactory bulb.
• It proceeds as olfactory tract, it ends at anterior
perforated substance and uncus.
• It by passes the thalamus and ends in the limbic
system.
• Injury to the anterior cranial fossa may damage these
nerves and leads to anosmia and CSF rhinorrhea
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5. Anosmia is the result after injury to the
cribriform plate of ethmoid
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6. II- Optic nerve
• It carries vision and color discrimination.
• Developmentally optic nerve and retina are
outgrowths of brain.
• Optic nerve arises from the rods/cones/bipolar
neurons of retina, optic nerve passes through the
optic canal and form optic chiasma, it follows as
optic tract and ends in the lateral geniculate
ganglion.
• Fibers arising from lateral geniculate ganglion are
projected to visual cortex area 17/18/19 calcarine
sulcus/occipital cortex.
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8. Lesions of optic pathways
• Complete lesion of optic nerve of one side leads to
complete blindness in the corresponding eye.
• Compression of optic chiasma causes bitemporal
hemianopia because the nasal fibers from both
sides are interrupted.
• Lesion of optic tract of one side leads to
corresponding nasal and contralateral temporal
hemianopia.
• Lesion of optic radiation of one side leads to
corresponding nasal and contralateral temporal
hemianopia
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9. III- Oculomotor nerve
• It supplies all extra ocular muscles except lateral rectus
and superior oblique.
• It is a purely motor nerve. Its nucleus is situated at the
superior colliculus level of mid brain, at the floor of
periaqueductal gray.
• It has an accessory nucleus situated medial to the main
nucleus, it is called as EW nucleus/Edinger Westphal
nucleus, it is parasympathetic nucleus for sphincter
pupillae.
• Oculomotor nerve appears at the interpeduncular fossa
and passes through the lateral wall of cavernous sinus
and enters the orbit through the SOF.
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10. Injury to oculomotor nerve result in
• Ptosis- drooping of the eyelid due to paralysis
of LPS
• External squint due to unopposed action of
lateral rectus and superior oblique.
• Mydriasis due to paralysis of sphincter
pupillae
• Diplopia- double vision
• Loss of accommodation & light reflex.
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11. IV- Trochlear nerve
• Its nucleus is situated at the inferior colliculus level
in the periaquaductal gray, it emerges dorsally and
enters the lateral wall of cavernous sinus and
supplies the superior oblique muscle.
• Injury to the IV nerve result in paralysis of superior
oblique, the affected eye rotates medially producing
diplopia.
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12. V- Trigeminal nerve
• It is a mixed cranial nerve , attached to the
basilar part of pons. It has a ganglion
Gasserian ganglion situated in the cavum
trigeminale. It divides into three roots, hence
its name.
• Ophthalmic V1
• Maxillary V2
• Mandibular V3
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13. There are four nuclei, one motor and 3
sensory for V nerve
•
•
•
•
•
Motor nucleus is situated at the pons.
Sensory nuclei are:Mesencephalic nucleus in the mid brain
Main sensory nucleus in the upper pons
Spinal nucleus in the lower pons, medulla and
upper cervical spinal cord.
• The V1 emerges through the SOF.
• The V2 pass through the foramen rotundum.
• The V3 exits through the foramen ovale.
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18. Cranial nerves in the lateral wall of
cavernous sinus
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19. VI – Abducent nerve
• Its nucleus is situated in the pons, at the facial
colliculus level in the floor of IV ventricle.
• Its fibers emerge at the pontomedullary
junction.
• The nerve passes through the lateral wall of
cavernous sinus and enters the orbit through
the SOF and supplies the lateral rectus.
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20. Applied anatomy
• In a lesion of the abducens nerve, the patient
cannot turn the eye laterally, causing internal
strabismus, diplopia.
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21. VII- Facial nerve
• It is motor to muscle of facial expression and
sensory to presulcal area of tongue and
secretomotor to submandibular and sublingual
glands.
• The motor nucleus is situated in the pons.
• Taste nucleus is the nucleus of tractus solitarius
situated in the medulla.
• The secretomotor fibers/ parasympathetic fibers
arises from superior salivatory nucleus situated
adjacent to DVN( dorsal vagal nucleus)
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22. The facial nerve exits through the
stylomastoid foramen
• The chorda tympani nerve emerges out through the
tympanosquamous fissure and joins the lingual
nerve in the infratemporal fossa, to be carried to
the presulcal area of tongue for special taste
sensations.
• The chorda tympani also carries secretomotor fibers
for submandibular/sublingual glands. The
preganglionic fibers get relayed at the
submandibular ganglion.
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23. Facial nerve injuries
• If the facial nucleus are affected, there may be damage
to abducent nucleus/lateral rectus palsy; motor
trigeminal nucleus may also be involved( paralysis of
muscles of mastication and sensory loss of face.
• Lesion at the internal acoustic meatus, resulting in loss
of taste from anterior part of tongue with ipsilateral
deafness and facial paralysis.
• Lesion at the facial canal, result in hyperacusis in one of
the ear.
• If the lesion is at the temporal bone, it result in loss of
taste from anterior third of tongue.
• Bell’s palsy if the lesion is at the stylomastoid foramen.
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24. Features of Bell’s palsy
• Facial asymmetry and affected side is immobile.
• The eyebrows are drooped, wrinkles are smoothed
out, palpebral fissure is widened
• Food accumulates in the cheek, from paralysis of
buccinator and dribbles.
• Platysma and auricular muscles are paralyzed
• Tears will flow over lower eyelid and saliva will
dribble from the corner of the mouth.
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25. Left facial nerve palsy
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27. VIII-Vestibulocochlear nerve
• It is a purely sensory
nerve.
• It is a dual nerve.
• There are four vestibular
nuclei situated in the
floor of VI ventricle.
• There are two cochlear
nuclei, dorsal and ventral
cochlear nuclei situated
dorsal and ventral to the
inferior cerebellar
peduncle.
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• The vestibulocochlear
nerve enter through the
internal acoustic canal
along with the facial
nerve and get attached
with the cochlea and
vestibular apparatus in
the internal ear.
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28. Disturbance of vestibular nerve
• Result in giddiness/vertigo and nystagmus.
• Vestibular nystagmus is an uncontrollable
rhthmic oscillation of the eyes.
• A patient with vestibular nerve injury cannot
walk in a straight line, with eyes closed.
• Disturbance of cochlear nerve produce
deafness and tinnitus.
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29. IX- Glossopharyngeal nerve
• It is a mixed cranial nerve. It exits through the jugular
foramen.
• It is nerve of III arch, it supplies stylopharyngeus,
secretomotor fibers to parotid gland and sensory fibers
to tonsil, pharynx and posterior 1/3rd of tongue and
special taste sensation from post sulcal area and
circumvallate papillae.
• The nuclei are :- 1. Nucleus ambiguus/medulla
• 2. Inferior salivatory nucleus for otic ganglion
• 3. Spinal nucleus of trigeminal nerve
• 4. Nucleus of tractus solitarius
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30. X- Vagus nerve
• It is a mixed cranial nerve, exits through jugular
foramen.
• Its nuclei are:• 1. Nucleus ambiguus – medulla
• 2. dorsal vagal nucleus-medulla
• 3. nucleus tractus solitarius – medulla
• 4. spinal nucleus of trigeminal nerve.
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31. XI – Accessory nerve
•
•
•
•
•
It has two roots, cranial and spinal.
Nuclei are:1. Nucleus ambiguus- medulla
2. Anterior horn cells of upper 6 cervical nerves.
Lesion of accessory nerve will result in paralysis of
sternomastoid/trapezius muscles; drooping of
shoulder, weakness& difficulty in raising the arm
above horizontal.
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32. XII- Hypoglossal nerve
• Its nucleus is situated in the medulla, the
hypoglossal triangle.
• The nerve leaves the cranial cavity through the
hypoglossal canal.
• It supplies all the tongue muscles except
palatoglossus.
• Injury result in unilateral lingual paralysis and
hemiatrophy.
• The tip of tongue deviates to the paralyzed side
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33. Right and left hypoglossal nerve palsy
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34. References
Essential Clinical anatomy- Keith
Moore-fourth edition(644-672)
• http://casereports.bmj.com/content/2009/bcr
.08.2008.0636.full
• http://12cranialnerves.wordpress.com/cranial
-nerve-12-hypoglossal-nerve/
• http://en.wikipedia.org/wiki/Bell's_palsy
• http://tsdocs.org/downloads/CranialNerves.p
df
• http://www.gwc.maricopa.edu/class/bio201/c
n/cranial.htm
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35. Sample MCQS
• Paralysis of 3rd, 4th and 6th cranial nerves
with involvement of ophthalmic division of
trigeminal, localizes the lesion to:
• A. Cavernous sinus
• B. Apex of orbit
• C. Brainstem
• D. Base of skull
• E. At Internal acoustic canal
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36. If both eyes turn in, which CN is likely
injured?
A. VI B. V.C.III D.IV. E.V
A dysfunction in which of
the following nerves
would cause anosmia?
A. I
B. II
C. III
D. IX
E. XI
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• Which CN is responsible
for salivation?
• A. IX
• B. XI
• C. XII
• D. IV
• E. III
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37. If someone had trouble with speech and swallowing and the
larynx, which nerve may be to blame?
A. IX.B.X.C.XI.D.XII E.VIII
• A balance dysfunction is
probably due to which
nerve:
• A. IV
• B. V
• C. VI
• D. VII
• E. VIII
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• Which cranial nerve is
responsible for
mastication?
• A. I
• B. II
• C.III
• D. IV
• E. V
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38. Sample MCQS
• A 50-year old man present with complaint of double
vision. While testing the patient's right eye movement
during a cranial nerve test, the physician noted that the
patient cannot elevate the adducted eye. Which of the
following muscles is involved?
• A. Superior rectus
• B. inferior rectus
• C. Lateral rectus
• D.Superior oblique
• E.Inferior oblique
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39. If someone could not produce tears, which CN may be
damaged?
A. Optic B. Oculomotor C.Facial D. Glossopharyngeal E. Vagus
• Which cranial nerve is called
as “Wanderer”?
• A. Vagus
• B. Glossopharyngeal
• C. Accessory
• D. Hypoglossal
• E.Facial
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• If the Optic nerve is cut at the
optic chaism, what kind of
deficit to vision will occur?
• A. Tunnel vision& Bitemporal
heteronymous hemianopia
• Bilateral blindness
• C.Monoocular blindness
• D. Contralateral homonymous
hemianopsia
• E. bitemporal homonymeous
blindness
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