Abducens nerve (CN VI)

The abducens nerve (Latin: nervus abducens), the sixth cranial nerve (CN VI), is a motor nerve that exclusively innervates one extraocular muscle of the eye, namely, the lateral rectus muscle.

Abducens nerve origin and course

The abducens nerve arises from neuronal cell bodies situated in the abducens nucleus. The nucleus is located in the dorsal pons - in the superior aspect of the rhomboid fossa below the facial colliculus. The sixth cranial nerve emerges from the ventral aspect of the brainstem at the caudal border of the pons in the pontomedullary junction (between the pons and pyramid of the medulla oblongata).

The abducens nerve then pierces through the dura mater covering the clivus of the occipital bone, runs upward in the Dorello canal between the dura mater and the skull, then bends sharply across the upper border of the petrous part of the temporal bone, and enters the cavernous sinus. The abducens nerve is the only cranial nerve traversing the cavernous sinus. Within the cavernous sinus, the abducens nerve lies just inferolateral to the internal carotid artery.

After passing through the sinus, the nerve enters the orbit through the superior orbital fissure within the common tendinous ring (annulus of Zinn) below the inferior division of the oculomotor nerve (CN III). The abducens nerve then passes forward to innervate one extraocular muscle - the lateral rectus muscle.