Inferior altitudinal hemianopia associated with a tumor in the posterior fossa: report of a case.

Altitudinal hemianopias may be related to chiasmatic involvement. A case in which horizontal inferior hemianopia is associated with a tumor in the posterior fossa producing a triventricular hydrocephalus is described. The visual field defect is interpreted as a consequence of the pressure by a dilated third ventricle upon the chiasmatic area.