Edinger–Westphal nucleus (oculomotor, CN III)
Preganglionic · CN III Midbrain
Midbrain nucleus at the level of the superior colliculus, dorsal to the main oculomotor nucleus. Preganglionic fibres travel in CN III, lying superficially in the nerve, and leave the inferior division with the branch to inferior oblique to reach the ciliary ganglion.
Traced from the start
- Parasympathetic (craniosacral) outflow
- Edinger–Westphal nucleus (oculomotor, CN III)
Detail
- Afferent input
- Pretectal nucleus projects bilaterally, so light in one eye constricts both pupils (consensual reflex)
- Position in CN III
- Pupillomotor fibres run dorsomedially and peripherally, supplied by pial vessels
- Route
- CN III → cavernous sinus lateral wall → superior orbital fissure → inferior division → nerve to inferior oblique → parasympathetic root of ciliary ganglion
When it goes wrong
Posterior communicating artery aneurysm or uncal herniation compressing CN III from outside
'Surgical' third nerve palsy: dilated unreactive pupil early, with ptosis and the eye deviated down and out — a fixed dilated pupil with falling GCS signals herniation
Diabetic or hypertensive microvascular infarction of the nerve core
'Medical' third nerve palsy: painful ptosis and ophthalmoplegia with a spared, reactive pupil because the superficial pupillomotor fibres keep their pial supply
Practise this structure
4 questions in the bank tagged Cranial Nerves.
A 52-year-old woman has had two months of numbness over the right forehead, the right upper eyelid and the tip of her nose, with a gritty feeling in the right e…
Foundations · middle twist
A 44-year-old man has had 18 months of worsening hearing on the left with constant ringing in that ear. He still follows conversation in a quiet room but cannot…
Foundations · middle twist
A 58-year-old man has sudden vertigo and a hoarse voice, and chokes when he drinks. The palate elevates to the right and there is no gag response when the left…
Foundations · middle twist
A 27-year-old man was struck on the head at football a week ago. He now sees two images, one above the other, worst when reading or going down stairs. The verti…
Foundations · middle twist