What is the route of cranial nerve 4?
Cranial nerve 4 travels posteriorly and medially, crosses the midline, wraps around the midbrain, and exits the brain stem laterally between the posterior cerebral artery and superior cerebellar artery.
It has the longest intracranial route (approximately 7.5 cm) of any cranial nerve.
It then travels through the cavernous sinus and enters the orbit through the superior orbital fissure.
Because it crosses the midline, the right trochlear nerve innervates the left superior oblique muscle.