Oculomotor nerve
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The oculomotor nerve is the third of the cranial nerves and arises from the midbrain. It is responsible for the movements of four of the six extraocular muscles, the other two being innervated by the trochlear and abducens nerves.
Gross anatomy
Nucleus and cisternal portion
The oculomotor nucleus lies in the deep periaqueductal grey matter at the level of the superior colliculus anterior to the cerebral aqueduct. The fibres run through the tegmentum, red nucleus and medial aspect of the substantia nigra to emerge from the medial aspect of the cerebral peduncle into the interpeduncular cistern. The nerve then travel forwards, below the posterior cerebral artery (where it can be compressed by a posterior communicating artery aneurysm) and above the superior cerebellar artery, before piercing the dura mater and entering the cavernous sinus.
Cavernous sinus portion
Within the cavernous sinus the oculomotor nerve is located uppermost, above the trochlear nerve in the lateral wall of the sinus.
Orbital portion
It enters the orbit via the superior orbital fissure as two branches: superior division and inferior division, with the nasociliary nerve (a branch of the ophthalmic division of the trigeminal nerve) between them and the abducens nerve (CN VI) below all three. These four branches pass through the tendinous ring.
Superior division
The superior division, the smaller of the two, runs above the optic nerve and gives branches to superior rectus and levator palpebrae superioris muscles which it supplies with motor fibres. Additionally it also supplies the latter with sympathetic fibres derived from the internal carotid artery.
Inferior division
The inferior division supplies the inferior rectus, medial rectus (this branch passes below the optic nerve), and the inferior oblique. It also gives off the parasympathetic root to the ciliary ganglion.
Related pathology
-<p>The<strong> oculomotor nerve </strong>is the third of the <a href="/articles/cranial-nerves">cranial nerves</a> and arises from the <a href="/articles/midbrain">midbrain</a>. It is responsible for the movements of four of the six <a href="/articles/extra-ocular-muscles">extraocular muscles</a>, the other two being innervated by the <a href="/articles/trochlear-nerve">trochlear</a> and <a href="/articles/abducens-nerve">abducens </a>nerves.</p><h4>Gross anatomy</h4><h5>Nucleus and cisternal portion</h5><p>The oculomotor nucleus lies in the deep <a href="/articles/periaqueductal-grey-matter-1">periaqueductal grey matter</a> at the level of the <a href="/articles/corpora-quadrigemina">superior colliculus</a> anterior to the <a href="/articles/cerebral-aqueduct-of-sylvius">cerebral aqueduct</a>. The fibres run through the <a href="/articles/tegmentum">tegmentum</a>, <a href="/articles/red-nucleus">red nucleus</a> and medial aspect of the <a href="/articles/substantia-nigra">substantia nigra</a> to emerge from the medial aspect of the <a href="/articles/cerebral-peduncles">cerebral peduncle</a> into the <a href="/articles/interpeduncular-cistern">interpeduncular cistern</a>. The nerve then travel forwards, below the <a href="/articles/posterior-cerebral-artery">posterior cerebral artery</a> (where it can be compressed by a <a href="/articles/posterior-communicating-artery">posterior communicating artery</a> aneurysm) and above the <a href="/articles/superior-cerebellar-artery">superior cerebellar artery</a>, before piercing the <a href="/articles/dura-mater">dura mater</a> and entering the <a href="/articles/cavernous-sinus">cavernous sinus</a>.</p><h5>Cavernous sinus portion</h5><p>Within the <a href="/articles/cavernous-sinus">cavernous sinus</a> the oculomotor nerve is located uppermost, above the <a href="/articles/trochlear-nerve">trochlear nerve</a> in the lateral wall of the sinus.</p><h5>Orbital portion</h5><p>It enters the orbit via the <a href="/articles/superior-orbital-fissure">superior orbital fissure</a> as two branches: superior division and inferior division, with the <a href="/articles/nasociliary-nerve">nasociliary nerve</a> (a branch of the ophthalmic division of the <a href="/articles/trigeminal-nerve">trigeminal nerve</a>) between them and the <a href="/articles/abducens-nerve-cn-vi">abducens nerve (CN VI)</a> below all three. These four branches pass through the <a href="/articles/tendinous-ring">tendinous ring</a>.</p><h6>Superior division</h6><p>The superior division, the smaller of the two, runs above the <a href="/articles/optic-nerve">optic nerve</a> and gives branches to <a href="/articles/superior-rectus">superior rectus</a> and <a href="/articles/levator-palpebrae-superioris">levator palpebrae superioris</a> muscles which it supplies with motor fibres. Additionally it also supplies the latter with sympathetic fibres derived from the <a href="/articles/internal-carotid-artery-1">internal carotid artery</a>.</p><h6>Inferior division</h6><p>The inferior division supplies the <a href="/articles/inferior-rectus">inferior rectus</a>, <a href="/articles/medial-rectus-muscle">medial rectus</a> (this branch passes below the <a href="/articles/optic-nerve">optic nerve</a>), and the <a href="/articles/inferior-oblique">inferior oblique</a>. It also gives off the parasympathetic root to the <a href="/articles/ciliary-ganglion">ciliary ganglion</a>.</p><h4>Related pathology</h4><ul><li><a href="/articles/oculomotor-nerve-palsy">oculomotor nerve palsy</a></li></ul>- +<p>The<strong> oculomotor nerve </strong>is the third of the <a href="/articles/cranial-nerves">cranial nerves</a> and arises from the <a href="/articles/midbrain">midbrain</a>. It is responsible for the movements of four of the six <a href="/articles/extraocular-muscles-1">extraocular muscles</a>, the other two being innervated by the <a href="/articles/trochlear-nerve">trochlear</a> and <a href="/articles/abducens-nerve">abducens </a>nerves.</p><h4>Gross anatomy</h4><h5>Nucleus and cisternal portion</h5><p>The oculomotor nucleus lies in the deep <a href="/articles/periaqueductal-grey-matter-1">periaqueductal grey matter</a> at the level of the <a href="/articles/corpora-quadrigemina">superior colliculus</a> anterior to the <a href="/articles/cerebral-aqueduct-of-sylvius">cerebral aqueduct</a>. The fibres run through the <a href="/articles/tegmentum">tegmentum</a>, <a href="/articles/red-nucleus">red nucleus</a> and medial aspect of the <a href="/articles/substantia-nigra">substantia nigra</a> to emerge from the medial aspect of the <a href="/articles/cerebral-peduncles">cerebral peduncle</a> into the <a href="/articles/interpeduncular-cistern">interpeduncular cistern</a>. The nerve then travel forwards, below the <a href="/articles/posterior-cerebral-artery">posterior cerebral artery</a> (where it can be compressed by a <a href="/articles/posterior-communicating-artery">posterior communicating artery</a> aneurysm) and above the <a href="/articles/superior-cerebellar-artery">superior cerebellar artery</a>, before piercing the <a href="/articles/dura-mater">dura mater</a> and entering the <a href="/articles/cavernous-sinus">cavernous sinus</a>.</p><h5>Cavernous sinus portion</h5><p>Within the <a href="/articles/cavernous-sinus">cavernous sinus</a> the oculomotor nerve is located uppermost, above the <a href="/articles/trochlear-nerve">trochlear nerve</a> in the lateral wall of the sinus.</p><h5>Orbital portion</h5><p>It enters the orbit via the <a href="/articles/superior-orbital-fissure">superior orbital fissure</a> as two branches: superior division and inferior division, with the <a href="/articles/nasociliary-nerve">nasociliary nerve</a> (a branch of the ophthalmic division of the <a href="/articles/trigeminal-nerve">trigeminal nerve</a>) between them and the <a href="/articles/abducens-nerve-cn-vi">abducens nerve (CN VI)</a> below all three. These four branches pass through the <a href="/articles/tendinous-ring">tendinous ring</a>.</p><h6>Superior division</h6><p>The superior division, the smaller of the two, runs above the <a href="/articles/optic-nerve">optic nerve</a> and gives branches to <a href="/articles/superior-rectus">superior rectus</a> and <a href="/articles/levator-palpebrae-superioris-muscle">levator palpebrae superioris</a> muscles which it supplies with motor fibres. Additionally it also supplies the latter with sympathetic fibres derived from the <a href="/articles/internal-carotid-artery-1">internal carotid artery</a>.</p><h6>Inferior division</h6><p>The inferior division supplies the <a href="/articles/inferior-rectus">inferior rectus</a>, <a href="/articles/medial-rectus-muscle">medial rectus</a> (this branch passes below the <a href="/articles/optic-nerve">optic nerve</a>), and the <a href="/articles/inferior-oblique">inferior oblique</a>. It also gives off the parasympathetic root to the <a href="/articles/ciliary-ganglion">ciliary ganglion</a>.</p><h4>Related pathology</h4><ul><li><a href="/articles/oculomotor-nerve-palsy">oculomotor nerve palsy</a></li></ul>
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