cranial nerves 1.pdf.. Presentation about cranial nerve

Presentation About cranial nerve

1. Cranial nerves
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2. Olfactory nerve
1
st
cranial nerve (functional component – SSA)
It is a sensory nerve which carries the sense of smell.
It begins as a dozen of filaments from the olfactory
mucosa of the nasal cavity.
These filaments pass thru the cribriform plate of ethmoid
to reach the olfactory bulb in the anterior cranial fossa.
Olfactory epithelium of nose --- olfactory rootlets --
Olfactory bulb --Olf. Tract -- lateral and medial olfact.
Stria
Lateral olfact. Stria --Pyriform lobe
Medial olfac. Stria - septal nuclei
Lesions of olfactory nerve result in loss of sense of smell
called anosmia.

3. Figure 8.48 Cranial nerves exiting the cranial cavity.
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4. Figure 8.49 Cranial nerves on the base of the brain.
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5. Figure 8.37 Arterial supply to the brain. A. Diagram.
Arterial supply to the brain. B. Magnetic resonance angiogram showing normal carotid and vertebral arteries. C. Enhanced CT scan of carotid vessels.
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6. Optic nerve
2
nd
cranial nerve. Purely a sensory nerve (SSA).
It is a nerve of sight.
It extends from the eyeball to the optic chiasma which lies above
the pituitary fossa.
Fibres of the optic nerve arise from retina and leave the eyeball at
the optic disc.
Fibres arising from the nasal half of the retina deccusate in optic
chiasma with fibres of the opp. side and then run along the optic
tract of the opp. side.
Fibres arising in the temporal half of retina do not deccusate in the
optic chiasma and thus run in the optic tract of the same side.
The fibres of the optic tract relay in the lateral geniculate body
From the lat geniculate body optic radiations arise and transfer the
information to the visual area of occipital lobe.

7. Figure 8.97 Ophthalmic nerve [V1] and its divisions.
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9. Visual pathway
Retina -- optic nerve --optic chiasma --
optic tract --lateral geniculate body --
optic radiations -- visual cortex.

10. Special features of optic nerve
It is not a true peripheral nerve, rather it is a tract of the
forebrain.
It is surrounded by meninges and thus by a
subarachnoid space containing CSF.
Its fibres are myelinated by oligodendrocytes and not by
schwann cells.
Lesion in retina leads to scotoma.
If optic nerve is damaged, there will be complete
blindness on the side of lesion.
Optic chiasma lesion if central leads to bitemporal
hemianopia; but if peripheral on both sides lead to
binasal hemianopia.

11. Occulomotor nerve
It is the 3
rd
cranial nerve.
It moves the eyeball.
Supplies most of the muscles of the
eyeball and plays a principal role in
accomodation.

12. Functional components
General somatic efferent fibres (GSE) : They
arise from the somatic component of
occulomotor nucleus and supply most of the
extrinsic muscles of eyeball.
General visceral efferent (GVE) : They arise from
the parasympathetic component (Edinger
westphal nucleus) of the occulomotor nucleus.
They are preganglionic parasympathetic fibres
that relay in the ciliary ganglion. The
postganglionic fibres from the ciliary ganglion
supply sphincter pupillae and ciliaris muscle of
the eyeball.

13. Course of occulomotor N.
It arises from occulomotor nucleus in the midbrain.
The nerve emerges from midbrain in the interpeduncular
fossa, then runs between the posterior cerebral and
superior cerebellar arteries, pierces the duramater near
the apex of petous temporal bone and travels forward in
the lateral wall of the CS.
In the anterior part of the CS it divides into 2
subdivisions which enter the orbit thru SOF.
The upper division supplies SR and LPS.
The lower division supplies IR, MR and IO muscles of
eyeball. The nerve to IO gives a motor root to the ciliary
ganglion.The post ganglionic fibres from the ciliary
ganglion supply the SP and ciliaris muscles.

14. Figure 8.49 Cranial nerves on the base of the brain.
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15. Figure 8.117 Grooves and hiatuses for the greater and lesser petrosal nerves.
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19. Applied anatomy
Nerve of accomodation – Occulomotor nerve
supplies all the muscles involved in
accomodation. This includes :
Medial rectus – causing convergence of eyes.
Sphincter pupillae – causing constriction of
pupil.
Ciliary muscle – making the lens more convex.
Damage leads to :
Ptosis (LPS paralysed), lateral squint (MR
paralysed), dilated pupil (sphincter pupillae
paralysed), loss of accomodation and diplopia.

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21. Trochlear nerve
4
th
cranial nerve.
Smallest cranial nerve.
Only cranial nerve to emerge on the dorsal
aspect of the brain.
Supplies only the SO muscle of the
eyeball.

22. Course and distribution
Trochlear nerve arises from the 4
th
nerve nucleus
in the midbrain.
Before emerging on the dorsal aspect its fibres
cross the midline.
It passes forwards between superior cerebellar
and posterior cerebral arteries.
It pierces the duramater to run in the lateral wall
of the CS.
It enters the orbit thru the SOF and supplies the
SO muscle.

23. Applied anatomy
Diplopia
Weakness of downward gaze – difficulty in
going down the stairs.
Squint.

24. Abducent nerve
6th
cranial nerve.
Motor nerve.
Supplies LR muscle of the eyeball.
Most susceptible to damage during raised
intracranial pressure

25. Functional components
GSE – to LR muscle.
GSA – proprioceptive impulses from the
muscle .

26. Course
It arises from the abducent nucleus in the lower part of
pons and emerges from the brain stem at the junction of
pons and medulla.
It runs upwards, forwards and laterally in the posterior
cranial fossa and crosses dorsal to the anterior inferior
cerebellar artery.
It crosses the petrous tempopral bone to reach the CS.
It entres the CS by piercing the posterior wall and lies
first lateral and then inferolateral to the ICA.
It enters the orbit thru the SOF and supplies the LR
muscle.

27. Figure 8.49 Cranial nerves on the base of the brain.
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28. Figure 8.117 Grooves and hiatuses for the greater and lesser petrosal nerves.
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29. Applied anatomy
Medial squint.
Diplopia while looking towards the
paralyzed side.

30. Trigeminal nerve
5
th
cranial nerve.
Largest cranial nerve.
Mixed nerve (mainly sensory).

31. Functional components
GSA – carry exteroceptive sensations
(pain, touch and temperature)from face
and head,mucous membrane of mouth
and nasal cavity.
- proprioceptive sensations muscles of
mastication.
SVE – are motor to muscles of
mastication, anterior belly of digastric,
mylohyoid, tensor palati and tensor
tympani.

32. Nuclei
Principal sensory nucleus – concerned with
general sensations of touch from face.
Spinal nucleus – concerned with
sensations of pain and temperature.
Mesencephalic nucleus – contains unipolar
neurons and receives proprioceptive
sensations from muscles of mastication.
Motor nucleus – gives efferent fibers for
muscles of mastication.

33. Course
The 5
th
cranial nerve arises from the ventral aspect of
pons by two roots – a large sensory and a small motor
root.
Motor root lies medial to the sensory root.
They pass forward in the PCF towards the apex of
petrous temporal bone.
The two roots enter the trigeminal cave on the anterior
aspect of petrous temporal bone – sensory root joins the
trigeminal ganglion while motor root passes deep to it.
The anterior convex part of the trigeminal ganglion gives
rise to three divisions of the trigeminal nerve –
ophthalmic, maxillary and mandibular.

34. Figure 8.49 Cranial nerves on the base of the brain.
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35. Ophthalmic nerve
Smallest of the three divisions.
Arises from the convex anterior border of the
trigeminal ganglion.
It pierces the duramater of the trigeminal cave
and entres the lateral wall of CS. In the anterior
part of CS it divides into
- lacrimal N
- frontal N
- nasociliary N
These nerves entre the orbit thru the SOF.

36. Figure 8.98 Relationship of the ophthalmic nerve [V1] and its divisions to the muscles of the eyeball.
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Lacrimal nerve
Smallest branch
In the orbit it
supplies the
lacrimal gland
Also gives
palpebral br to
skin of upper
eyelid
Frontal nerve
In the orbit it
runs above the
LPS muscle.
Ends by
dividing into two
branches
- SO
- ST
Nasociliary nerve
In the orbit it
runs forwards
and medially
above the optic
nerve
. At the medial
wall it divides
into branches.
- Br to ciliary
ganglion
Long ciliary-
nerves to ciliary
body.
AE, PE and IT-
br

39. Maxillary nerve
It is a sensory nerve.
It arises from the anterior convex part of trigeminal
ganglion in the MCF.
Passes forwards to entre the CS .
It leaves the MCF by passing thru the F rotundum to
entre the pyerygopalatine fossa.
The nerve crosses the fossa and entres the orbit by
passing thru the Inferior Orbital Fissure.
In the orbit it is called as IO nerve.
The nerve then runs in the IO groove -- IO canal and
finally appears on the face by emerging thru the IOF.

40. Branches (maxillary nerve)
In the MCF – meningeal br
In the PP fossa – ganglionic br (to PP gang.)
- zygomatic br -- divides into ZF & ZT
- posterior superior alveolar (upper molars)
In the orbit – middle superior alveolar (upper premolars)
- anterior superior alveolar (upper incissors
and canines)
On the face – palpebral (lower lid)
- nasal
- labial (upper lip)

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42. Mandibular nerve
Largest of the three divisions of 5
th
nerve.
Consists of both sensory and motor fibres.
Functional components include SVE and GSA fibres.
The mandibular nerve arises from the trigeminal
ganglion and entres the infratemporal fossa thru the FO.
In the FO, it is joined by the motor root of the 5
th
nerve
and emerges from the skull as a mixed nerve.
In the IT fossa it soon divides into anterior and posterior
divisions.

43. Branches (mandibular nerve)
Br from the trunk
- meningeal br
- N. to MP
Br from anterior div. 
- DT
- Masseteric
- N. to LP
- Buccal nerve
Br from posterior div.
- Auriculotemporal N.
- Lingual N
- Inferior alveolar N.

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45. Figure 8.58 Trigeminal nerve [V] leaving the skull.
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46. Lingual nerve
It is the smaller terminal branch of
posterior division. It is sensory to the
mucus membrane of anterior 2/3 of
tongue. In its course it is closely related to
third molar and near its termination to the
submandibular duct.
Applied anatomy - Lingual nerve is at
great risk during the surgical removal of
impacted third molar tooth.

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The nerve is at risk during removal of the
submandibular gland, during which the
submandibular duct must be dissected out
carefully.

48. Inferior alveolar nerve
One of the terminal br of posterior div. of
mandibular nerve.
It runs vertically downwards lateral to
medial pterygoid.
It entres the mandibular foramen and runs
in the mandibular canal.

49. Figure 8.139 Mandibular nerve [V3]-posterior trunk. A. Lateral view.
Mandibular nerve [V3]-posterior trunk. B. Anterior view. C. Anteromedial view.
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50. Branches (inferior alveolar N.)
Mylohyoid br. ( supplies the mylohyoid M.
and ant. Belly of digastric)
Dental br – to molars and premolars.
Insicive br – canine and incisor teeth.
Mental nerve – emerges at the mental
foramen and supplies skin of the chin and
lower lip.

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Inferior alveolar nerve block – most
common block performed in dentistry to
carry out dental procedures on the
mandibular teeth. The anaesthetic agent is
injected slightly superior to its entry into
the mandibular foramen. If the needle is
inserted too far posteriorly it may enter
the parotid gland and damage the facial
nerve leading to transient facial palsy.

52. Applied anatomy
Trigeminal neuralgia (tic douloureux) is a
severe excruciating pain of sudden onset
and short duration in the area of
distribution of one or more of the three
divisions of trigeminal nerve. The pain is
often initiated by touching a trigger area.
The most commonly involved divisions are
maxillary and mandibular nerves.
It is often associated with dental caries.

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Ophthalmic nerve supplies cornea,
conjunctiva, upper eyelid, forehead, nose
and anterior part of the scalp. Lesion
results in paraesthesia over the forehead
and nose. There is loss of corneal reflex.
Maxillary nerve supplies the skin of the
cheek, lateral aspect of nose, upper lip
and upper teeth. Lesion results in
paraesthesia and loss of sneeze reflex.

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Mandibular nerve provides sensory
innervation to the skin over the mandible,
auricle, lower lip and teeth. Lesion results
in paraesthesia along the mandible and
lower teeth and loss of jaw jerk.
Referred pain – It is the pain referred from
one br of the mandibular nerve to the
other. The pain of tongue cancer (lingual
nerve) is referred to the temporal region
(auriculotemporal nerve).

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Frey’s syndrome – It is a complication that
occurs when AT and Gr Auricular nerves
are cut by a wound or incision in the
parotid region.
When the patient eats beads of
prespiration appears on the face in the
parotid region. When the fibers of the
above nerves are cut , during the process
of regeneration the parasympathetic
secretomotor fibers of the AT nerve

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- destined to supply the parotid gland
grow out and join the fibers of the Gr.
Auricular nerve meant to supply the sweat
glands. When the person eats stimulus
intended for saliva production, produces
sweat secretion instead.