What are the main functions of the oculomotor nerve (CN III)?

The oculomotor nerve has two primary functions: motor control of most extraocular muscles for eye movement and eyelid elevation, and parasympathetic control for pupillary constriction and lens accommodation.

Which muscles does the oculomotor nerve innervate?

It innervates five muscles: superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris for eyelid elevation.

What happens if the oculomotor nerve is damaged?

Damage leads to symptoms including ptosis (drooping eyelid), lateral strabismus (eye deviates outward), dilated and fixed pupil, loss of accommodation, and diplopia (double vision).

What is the role of the Edinger–Westphal nucleus in the oculomotor nerve?

The Edinger–Westphal nucleus provides parasympathetic fibers that travel to the ciliary ganglion, ultimately controlling pupillary constriction and lens accommodation.

How does the oculomotor nerve travel from the brain to the eye?

It emerges from the midbrain, passes through the cavernous sinus, and enters the orbit via the superior orbital fissure, where it splits into upper and lower branches to supply muscles.

What causes oculomotor nerve paralysis?

Common causes include compression by aneurysms (e.g., from posterior communicating or internal carotid arteries), uncal herniation, or trauma.

Why does oculomotor nerve damage cause a dilated pupil?

Damage disrupts the parasympathetic fibers that normally constrict the pupil via the sphincter pupillae muscle, leaving the dilator pupillae unopposed, resulting in a dilated and fixed pupil.

Oculomotor Nerve (CN III) – Eye Movements & Pupillary Reflex

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