about 3rd cranial nerve.

1. Cranial Nerves
Oculomotor Nerve
Presented By:
Kiran Suwal

2. Cranial Nerves
• Cranial nerves are the nerves that emerge directly from the brain (including the brainstem),
in contrast to spinal nerves (which emerge from segments of the spinal cord).
• Cranial nerves relay information between the brain and parts of the body, primarily to and
from regions of the head and neck.
• There are 12 pairs of cranial nerves emerging directly from the brain.
• Sometime there may be a thirteenth cranial nerve, the terminal nerve (nerve O or N), which
is very small and may or may not be functional in humans
• Cranial Nerves may be sensory, motor or both and somatic or parasympathetic, or have
mixed functions.
• As a rule, cranial nerves do not cross in the brain.
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3. Types of Cranial Nerves
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4. Types of Cranial Nerves (Cont.…..)
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5. Types of Cranial Nerves (Cont.…..)
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6. Location of Cranial Nerves
• The olfactory and optic nerves arise from the anterior portion of the brain
called the cerebrum.
• The oculomotor and trochlear cranial nerves stem from the midbrain.
• The trigeminal, abducent, and facial nerves arise in the pons.
• The vestibulocochlear nerve arises in the inner ears and goes to the pons.
• The glossopharyngeal, vagus, accessory and hypoglossal nerves are attached
to the medulla
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9. Oculomotor Nerves
• The oculomotor nerve is the third cranial nerve.
• It offers motor and parasympathetic innervation to many of the ocular structures.
• It is distributed to the extraocular as well as the intraocular muscles.
• Medical Definition of oculomotor nerve : either nerve of the third pair of
cranial nerves that are motor nerves with some associated autonomic fibers, arise
from the midbrain, supply muscles of the eye except the superior oblique and the
lateral rectus with motor fibers, and supply the ciliary body and iris with autonomic
fibers by way of the ciliary ganglion—called also third cranial nerve
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11. Origin of Oculomotor Nerves
• The oculomotor nerve originates from the anterior aspect of the midbrain.
• It is situate in the ventromedial part of central grey matter of midbrain at the
level of superior colliculus.
• The fibers for the constrictor pupillae and for the ciliaris arise from the
Edinger-Westphal nucleus which forms part of the oculomotor nuclear
complex.
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12. Pathway of Oculomotor Nerves
• It moves anteriorly, passing below the posterior cerebral artery, and above the
superior cerebellar artery.
• The nerve pierces the dura mater and enters the lateral aspects of the cavernous
sinus.
• Within the cavernous sinus, it receives sympathetic branches from the internal
carotid plexus.
• The nerve leaves the cranial cavity via the superior orbital fissure.
• At this point, it divides into superior and inferior branches.
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13. Pathway of Oculomotor Nerves (Cont…..)
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• Superior branch: Motor innervation to the superior rectus and levator
palpabrae superioris. Sympathetic fibres run with the superior branch to
innervate the superior tarsal muscle.
• Inferior branch: Motor innervation to the inferior rectus, medial rectus and
inferior oblique. Parasympathetic fibres to the ciliary ganglion, which
ultimately innervates the sphincter pupillae and ciliary muscles.

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16. Functions of Oculomotor Nerves
• General somatic efferent, for movements of the eyeball.
• General visceral efferent or parasympathetic, for contraction of pupil and
accommodation.
• General somatic afferent column carries proprioceptive fibers from the
extraocular muscles to mesencephalic nucleus of V.
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17. Clinical Test of Oculomotor Nerves
• Cranial nerves III, IV, and VI are usually tested together as part of
the cranial nerve examination.
• Oculomotor nerves can be tested by following two ways:
 Eye muscles
 Pupillary reflexes
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21. Disorders of Oculomotor Nerves
• Complete and total paralysis of the third nerve results in:
Ptosis, i.e. Drooping of the upper eyelid
Lateral squint
Dilatation of the pupil
Loss of accommodation
Slight proptosis, i.e. Forward projection of the eye
Diplopia or double vision.
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22. Disorders of Oculomotor Nerves (Contd….)
• A midbrain lesion causing contralateral hemiplegia and ipsilateral paralysis of
the third nerve is known as Weber's syndrome.
• Supranuclear paralysis of the third nerve causes loss of conjugate
movement of the eyes.
• Compression of III nerve due to extradural haematoma causes dilatation
of pupil. Parasympathetic fibers lying superficial get affected first. Pupil
dilates on affected side and there s little response to light.
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23. Treatment of Disorders of Oculomotor Nerves
• Symptomatic cases can be treated with Strabismus surgery.
• Surgical correction of ptosis: Ptosis surgery
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