Trochlear and abducens nerve (English)

The trochlear nerve (CN IV) arises from the nucleus of trochlear nerve (containing general somatic efferent (GSE) neurons), which is located in the tegmentum of the caudal midbrain. Fibers from this nucleus decussate posteriorly and emerge from the dorsal midbrain, just below the inferior colliculus. From here, the trochlear nerve curves around the midbrain, passing through the lateral wall of the cavernous sinus, superior and lateral to the oculomotor nerve. It continues into the orbit via the superior orbital fissure, external to the common tendinous ring, before terminating in the superior oblique muscle.The abducens nerve (CN VI) arises from the nucleus of abducens nerve, which also contains general somatic efferent (GSE) neurons and is located near the rhomboid fossa/floor of the fourth ventricle. Fibers from this nucleus exit the brainstem at the medullopontine sulcus (pontomedullary junction) as the abducens nerve, which courses through the cavernous sinus (along the internal carotid artery). It then enters the orbit via the superior orbital fissure, internal to the common tendinous ring. The abducens nerve then penetrates the medial surface of the lateral rectus muscle, which functions as an abductor of the eyeball.