Opticosensory ataxia and alien hand syndrome after posterior cerebral artery territory infarction.

A right-handed woman developed left homonymous hemianopia and left hemianesthesia from infarction due to right posterior cerebral artery occlusion. Ataxia of the left arm and leg was severe and was not improved by vision. The patient often interpreted spontaneous movements of the left arm as alien in origin. The ataxia may have been caused by a combination of sensory ataxia, resulting from right thalamic infarction, and crossed-optic ataxia, resulting from posterior disconnection of the hemispheres due to right temporo-occipital infarction. This opticosensory ataxia was associated with a new form of "alien hand" syndrome.