Posterior cortical atrophy.

Two patients had a steadily progressive disorder of higher cortical function dominated by the early development of cortical visual deficits. In one, a right visual inattention progressed over a period of 2 years to a complete right homonymous hemianopia and relative left inferior quadrantanopia. In the second case, blind in the left eye for unrelated reasons, a temporal field loss was noted at presentation in the right eye, with the subsequent development of field loss in the inferior nasal quadrant on that side. Features of Balint's syndrome developed in both patients, with sticky fixation, ocular dysmetria and simultanagnosia. Prominent associated features were progressive dysmnesia, dyscalculia, ideomotor apraxia and spatial disorientation. Abstract reasoning, speech function and insight were all well preserved. MRI and CT scans revealed no focal abnormalities. These cases are similar to the 5 recently described by Benson et al. The pathological basis is unknown but may be an atypical form of Alzheimer's disease.