The trochlear nerve (/ ˈ t r ɒ k l ɪər /), [1] (lit. pulley-like nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates a single muscle - the superior oblique muscle of the eye (which operates through the pulley-like trochlea).Unlike most other cranial nerves, the trochlear nerve is exclusively a motor nerve (somatic efferent nerve).

Trochlear nucleus: This is the part of your trochlear nerve closest to your brain.It’s near the top of your brainstem. Ambient cistern: This area is near your brain’s outer protective tissue (the dura mater, which is part of your meninges).; Cavernous sinus: This is a hollow space in the middle of your skull.; Orbit: This is the bony socket of your skull that houses your eyeball.