Nerve
Oculomotor nerve (CN III)
Moves the eye and lifts the lid
High-yield
Palsy → 'down and out' eye, ptosis, and a dilated pupil (parasympathetic fibres run on the surface - compressed early by aneurysm/herniation).
Overview
The third cranial nerve, supplying four of the six extraocular muscles, the levator palpebrae, and (parasympathetically) pupil constriction and lens accommodation.
Learning this group? Read How to memorize the cranial nerves.
Reference facts
- Roots
- Motor and parasympathetic (cranial nerve)
- Course
- Emerges from the midbrain, passes through the cavernous sinus and superior orbital fissure into the orbit
- Motor
- Superior, inferior, and medial recti; inferior oblique; levator palpebrae superioris; (parasympathetic) sphincter pupillae and ciliary muscle
- Sensory
- No cutaneous sensory territory - this nerve is purely motor.
Clinical correlation
A blown (fixed, dilated) pupil signals compressive CN III palsy from uncal herniation until proven otherwise.
Frequently asked questions
What type of nerve is the oculomotor nerve (CN III)?
The oculomotor nerve (CN III) is motor and parasympathetic (cranial nerve).
What muscles does the oculomotor nerve (CN III) supply?
The oculomotor nerve (CN III) supplies the superior, inferior, and medial recti; inferior oblique; levator palpebrae superioris; (parasympathetic) sphincter pupillae and ciliary muscle.
What is the sensory distribution of the oculomotor nerve (CN III)?
No cutaneous sensory territory - this nerve is purely motor.
What is the course of the oculomotor nerve (CN III)?
Emerges from the midbrain, passes through the cavernous sinus and superior orbital fissure into the orbit.