Cranial Nerve III Palsy

The third cranial nerve is also known as oculomotor nerve and has 2 major components: Outer parasympathetic fibers that supply the ciliary muscles and the sphincter pupillae. Inner somatic fibers that supply the levator palpebrae superioris in the eyelid (which retracts the upper eyelid) and the 4 extraocular muscles (superior, middle, inferior recti, and inferior oblique). LR6(SO4)3 is a simple mnemonic representing the innervation of the extraocular muscles. It stands for: LR6: Lateral rectus muscle which is supplied by the sixth cranial nerve. SO4: Superior oblique muscle which is supplied by the fourth cranial nerve 3: The third cranial nerve supplies other extraocular muscles.