[Posterior cortical atrophy--a new dementia syndrome or a form of Alzheimer's disease?].

Posterior Cortical Atrophy (PCA) is a neurodegenerative disorder initially dominated by disturbances in higher visual functions including object agnosia, prosopagnosia, alexia, environmental agnosia and Balint's syndrome. Language, memory, insight, and judgement remain relatively preserved until late in the course. A characteristic neuroradiological finding consists of focal bilateral parieto-occipital atrophy demonstrated on MRI and CT. It was speculated that the possible underlying pathologic condition could be an atypical clinical variant of Alzheimer's disease, a lobar atrophy analogous to Pick's disease, a variant of Creutzfeldt-Jakob disease or some previously unrecognized entity. The prognostic question whether the visual agnostic symptoms are only a precursor of generalized dementia remained unsolved. The neuropsychological symptoms in these patients indicate that the occipitoparietal cortex is bilaterally affected which is in contrast to the parietotemporal distribution of lesions in Alzheimer's disease and the frontotemporal type of distribution in Pick's disease. The aim of this study was to review and analyze all cases of posterior cortical atrophy which have been reported in the literature. Up to now 58 cases of posterior cortical atrophy have been described. The first report of such a patient was given by A. Pick in 1902. The results of our analysis show that posterior cortical atrophy is mainly a presenile disorder which in most cases heralds the development of generalized dementia. The histopathological results suggest that the combination of clinical findings referred to as PCA can result from strikingly different pathological entities. However, most cases of PCA which were investigated postmortem revealed the histopathological lesion type of Alzheimer's disease. This suggests that PCA is rather a subgroup of Alzheimer's disease than an independent disease. This conclusion has some implication for the nosological classification of other localized slowly progressive syndromes such as slowly progressive aphasia. These syndromes may as well define possible clinical subgroups of the "classical" dementias. They show that the close relationship between the clinical profile and the brain regions involved does not necessarily imply a specific neuropathological process but focus the attention on the selective vulnerability of distinct neuronal systems.