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Posterior cortical atrophy: a new clinical entity, or Alzheimer's disease?

To the Editor. —Benson et al 1 in the July 1988 issue of theArchivespropose the existence of "posterior cortical atrophy" on the basis of case descriptions of five patients. They argue the following: "These cases are sufficiently similar to each other and... sufficiently different from those typical for either Alzheimer's or Pick's disease to warrant classing them separately until definitive pathologic information becomes available." We believe that, although the construct seems attractive and the radiologic evidence supportive, the data presented do not justify the proposal of a new clinical entity. The authors base their argument on the following major observations: (1) presence of prominent visual deficits and (2) relative preservation of memory, insight, and judgment. The visual deficits in their patients included ocular dysmetria, sticky fixation, simultanagnosia, and visual agnosia. Such deficits, plus others (dyschromatopsia, abnormal visual evoked potentials, prosopagnosia, and loss of contrast sensitivity) have been well-documented