Dilatation of pupils in a 'top of the basilar' stroke. Case report.

A case is presented of a 'top of the basilar' stroke followed by a well circumscribed midbrain lesion mainly involving the parenchyma around both third nerve nuclear complexes. Prominent clinical features were: third nerve paralysis including huge pupils unresponsive to light, transient unconsciousness, and slight cerebellar dyscoordination.