Edinger-Westphal nucleus

The Edinger-Westphal nucleus is the accessory parasympathetic cranial nerve nucleus of the oculomotor nerve (cranial nerve III), supplying the constricting muscles of the iris. The paired nuclei are posterior to the main motor nucleus and anterolateral to the cerebral aqueduct in the rostral midbrain at the level of the superior colliculus. It is the most rostral of the parasympathetic nuclei in the brain stem.

The Edinger-Westphal nucleus supplies preganglionic parasympathetic fibers to the eye, constricting the pupil and accommodating the lens.

The nucleus is named for both Ludwig Edinger, who demonstrated it in the fetus in 1885, and for Karl Friedrich Otto Westphal, who demonstrated it in the adult in 1887.