Midbrain corectopia.

Intermittent corectopia was recently observed in a patient with bilateral, rostral midbrain infarction. Results from neuropathologic examination disclosed isolated but intact Edinger-Westphal nuclei. An explanation of midbrain corectopia centered on segmental innervation of the pupil by the Edinger-Westphal nucleus. In the presence of a paralyzed dilator muscle, select, central inhibition of sphincter tone resulted in an oval and eccentric pupil.