The Edinger-Westphal nucleus is the parasympathetic part of the oculomotor nuclear complex. Its preganglionic fibres travel with cranial nerve III to the ciliary ganglion, which then supplies the muscles that constrict the pupil and focus the lens for near vision.
| Location | Upper midbrain, just dorsal to the main oculomotor nucleus, near the midline |
|---|---|
| Parts |
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| Connections |
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| Blood Supply | Paramedian perforators from the basilar tip and posterior cerebral artery |
Drives pupil constriction in the light reflex and pupil constriction plus lens accommodation during the near response.
Because input reaches the Edinger-Westphal nuclei from both pretectal areas, light in one eye constricts both pupils (direct and consensual reflexes). Dorsal midbrain lesions cause light-near dissociation, with pupils that react to near effort but not to light. Compression of the parasympathetic fibres in the third nerve by an aneurysm causes a fixed dilated pupil.
Pupils that constrict for near vision but poorly to light, seen with dorsal midbrain lesions and in Argyll Robertson pupils.
A dilated, unreactive pupil from compression of the parasympathetic fibres travelling from this nucleus, often from a posterior communicating artery aneurysm.
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