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
• Injury to the anterior cranial fossa may damage these
nerves and leads to anosmia and CSF rhinorrhea
Anosmia is the result after injury to the
cribriform plate of ethmoid
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
• Fibers arising from lateral geniculate ganglion are
projected to visual cortex area 17/18/19 calcarine
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
• Lesion of optic radiation of one side leads to
corresponding nasal and contralateral temporal
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
• 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
• Oculomotor nerve appears at the interpeduncular fossa
and passes through the lateral wall of cavernous sinus
and enters the orbit through the SOF.
Injury to oculomotor nerve result in
• Ptosis- drooping of the eyelid due to paralysis
• External squint due to unopposed action of
lateral rectus and superior oblique.
• Mydriasis due to paralysis of sphincter
• Diplopia- double vision
• Loss of accommodation & light reflex.
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
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
• Ophthalmic V1
• Maxillary V2
• Mandibular V3
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.
Cranial nerves in the lateral wall of
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
• The nerve passes through the lateral wall of
cavernous sinus and enters the orbit through
the SOF and supplies the lateral rectus.
• In a lesion of the abducens nerve, the patient
cannot turn the eye laterally, causing internal
VII- Facial nerve
• It is motor to muscle of facial expression and
sensory to presulcal area of tongue and
secretomotor to submandibular and sublingual
• 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)
The facial nerve exits through the
• 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
• The chorda tympani also carries secretomotor fibers
for submandibular/sublingual glands. The
preganglionic fibers get relayed at the
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
• 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.
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.
• It is a purely sensory
• 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
• 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.
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.
IX- Glossopharyngeal nerve
• It is a mixed cranial nerve. It exits through the jugular
• 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
• 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
X- Vagus nerve
• It is a mixed cranial nerve, exits through jugular
• Its nuclei are:• 1. Nucleus ambiguus – medulla
• 2. dorsal vagal nucleus-medulla
• 3. nucleus tractus solitarius – medulla
• 4. spinal nucleus of trigeminal nerve.
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
XII- Hypoglossal nerve
• Its nucleus is situated in the medulla, the
• The nerve leaves the cranial cavity through the
• It supplies all the tongue muscles except
• Injury result in unilateral lingual paralysis and
• The tip of tongue deviates to the paralyzed side
Right and left hypoglossal nerve palsy
• 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
If both eyes turn in, which CN is likely
A. VI B. V.C.III D.IV. E.V
A dysfunction in which of
the following nerves
would cause anosmia?
• Which CN is responsible
• A. IX
• B. XI
• C. XII
• D. IV
• E. III
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
• A. IV
• B. V
• C. VI
• D. VII
• E. VIII
• Which cranial nerve is
• A. I
• B. II
• D. IV
• E. V
• 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
If someone could not produce tears, which CN may be
A. Optic B. Oculomotor C.Facial D. Glossopharyngeal E. Vagus
• Which cranial nerve is called
• A. Vagus
• B. Glossopharyngeal
• C. Accessory
• D. Hypoglossal
• If the Optic nerve is cut at the
optic chaism, what kind of
deficit to vision will occur?
• A. Tunnel vision& Bitemporal
• Bilateral blindness
• C.Monoocular blindness
• D. Contralateral homonymous
• E. bitemporal homonymeous
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