Edinger-Westphal nucleus

Last revised by Craig Hacking on 13 Oct 2022

The Edinger-Westphal nucleus is a small parasympathetic motor nucleus in the midbrain and one of the two nuclei for the oculomotor nerve. It is one of the cranial nerve nuclei.

Gross Anatomy

The nucleus is located in the central midbrain at the level of the superior colliculus ventral and medial periaqueductal grey matter. It lies immediately dorsal to the larger oculomotor nucleus and just cranial to the trochlear nucleus.

Efferent fibers leave the nucleus ventrally joining fibers from the oculomotor nucleus and pass medially to or through the red nucleus and emerge from the medial aspect of the cerebral peduncles.


The parasympathetic fibers synapse in the ciliary ganglion and postganglionic fibers continue to the globe via the short ciliary nerves to innervate the constrictor pupillae muscle and ciliary body. It is therefore important in the functioning of the pupillary light and accommodation reflexes.

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Cases and figures

  • Figure 1: midbrain anatomy
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