![]() ' Down and out' position of the eye at rest - due to paralysis of the superior, inferior and medial rectus, and the inferior oblique (and therefore the unopposed activity of the lateral rectus and superior oblique).Ptosis (drooping upper eyelid) - due to paralysis of the levator palpabrae superioris and unopposed activity of the orbicularis oculi muscle.Clinical Relevance: Oculomotor Nerve Palsy Inferior branch - provides motor innervation to the inferior rectus, medial rectus and inferior oblique. ![]() Superior branch - provides motor innervation to the superior rectus and levator palpabrae superioris.It emerges from the anterior aspect of the midbrain, passing inferiorly to the posterior cerebral artery and superiorly to the superior cerebellar artery. The oculomotor nerve originates from the oculomotor nucleus - located within the midbrain of the brainstem, ventral to the cerebral aqueduct. Sympathetic - No direct function, but sympathetic fibres run with the oculomotor nerve to innervate the superior tarsal muscle (helps to raise the eyelid).Parasympathetic - Supplies the sphincter pupillae and the ciliary muscles of the eye.Motor - Innervates the majority of the extraocular muscles (levator palpebrae superioris, superior rectus, inferior rectus, medial rectus and inferior oblique).In this article we shall look at the anatomy of the oculomotor nerve - its anatomical course, functions and clinical correlations. It provides motor and parasympathetic innervation to some of the structures within the bony orbit. The oculomotor nerve is the third cranial nerve (CN III). Dilated pupil – due to the unopposed action of the dilator pupillae muscle.The patient is unable to elevate, depress or adduct the eye.‘ Down and out‘ position of the eye at rest – due to paralysis of the superior, inferior and medial rectus, and the inferior oblique (and therefore the unopposed activity of the lateral rectus and superior oblique).Ptosis (drooping upper eyelid) – due to paralysis of the levator palpabrae superioris and unopposed activity of the orbicularis oculi muscle.Therefore, the clinical features of CN III injury are associated with the eye: The oculomotor nerve provides motor and parasympathetic innervation to some of the structures within the bony orbit. Note: there are other pathological causes of oculomotor nerve palsy such as diabetes, multiple sclerosis, myasthenia gravis and giant cell arteritis. Posterior communicating artery aneurysm.Raised intracranial pressure (compresses the nerve against the temporal bone).The most common structural causes include: Oculomotor nerve palsy is a condition resulting from damage to the oculomotor nerve. Also supplies pre-ganglionic parasympathetic fibres to the ciliary ganglion, which ultimately innervates the sphincter pupillae and ciliary muscles.Ĭlinical Relevance: Oculomotor Nerve Palsy.Inferior branch – provides motor innervation to the inferior rectus, medial rectus and inferior oblique.Sympathetic fibres run with the superior branch to innervate the superior tarsal muscle.Superior branch – provides motor innervation to the superior rectus and levator palpabrae superioris.The nerve leaves the cranial cavity via the superior orbital fissure. At this point, it divides into superior and inferior branches: Within the cavernous sinus, it receives sympathetic branches from the internal carotid plexus. These fibres do not combine with the oculomotor nerve – they merely travel within its sheath. The nerve then pierces the dura mater and enters the lateral aspect of the cavernous sinus. The oculomotor nerve originates from the oculomotor nucleus – located within the midbrain of the brainstem, ventral to the cerebral aqueduct.
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