abducen

The abducens nerve, or nervus abducens, is the sixth cranial nerve. It is a motor nerve that innervates the lateral rectus muscle of the eye, enabling horizontal abduction (outward movement). By coordinating with other oculomotor pathways, it plays a central role in conjugate horizontal gaze.

Its cell bodies reside in the abducens nucleus in the dorsal pons. The nerve fibers emerge at the pontomedullary junction, traverse the subarachnoid space, and pass through the cavernous sinus. Within the orbit, the nerve enters via the superior orbital fissure and divides to supply the lateral rectus muscle.

Because of its long intracranial course, the abducens nerve is vulnerable to injury from increased intracranial pressure, trauma to the skull base, or microvascular disease. Lesions typically cause ipsilateral abduction weakness, producing horizontal diplopia that worsens when gazing toward the affected side; the eye may rest in a more inward (esotropic) position.

Clinical assessment focuses on gaze palsy and abduction limitation, often accompanied by diplopia. The nerve contains only motor fibers and has no parasympathetic component. The abducens nucleus communicates with the contralateral oculomotor nucleus via the medial longitudinal fasciculus to coordinate conjugate gaze.

Historically, the nerve derives its name from its function of abducting the eye; in medical Latin it is referred to as nervus abducens. It is one of the twelve cranial nerves and is a fundamental subject in anatomy and clinical neurology.