Objective: Posterior Cortical Atrophy (PCA) is a rare degenerative condition of unclear etiology and nosology. The number of cases reported is below 100, and the number of autopsied cases is very limited. The nosological relationship of PCA to Alzheimer's and Pick's Disease and to other forms of lobar atrophy remains unclear. We present a series of ten consecutive new cases with clinical, neuropsychological and imaging data.
Design: Clinical case series. PCA was diagnosed if pronounced parietal and/or occipital atrophy was shown by structural imaging. Emphasis is placed on Positron Emission Tomography findings obtained in seven cases and analyzed by Statistical Parametric Mapping (SPM).
Materials and Methods: Patients were followed over a mean time of 6.4 years. MRI was performed in all patients. 15 fluor-deoxy-glucose PET was performed in seven patients after a mean delay of 3.4 years post-onset. SPM analysis was performed for individual PCA patients, as well as for the entire group, and compared to a normal data base, according to a standard protocol (SPM99, Wellcome Department of Cognitive Neurology).
Results: There were eight men and two women. The mean age of onset was 55.3 years. At onset, eight patients had visuo-spatial and eight had memory impairment. A minority showed early signs of occipital lobe involvement with agnosia or hemianopia. Early symptoms of aphasia and frontal lobe impairment were missing or just minor, except for one patient who presented with psychosis and fronto-parietal atrophy, and was diagnosed to have Pick's disease. Six of seven patients who were observed for = 5 years become demented after a mean course of four years. SPM analysis of seven patients with PET showed hypometabolic areas that centered on the parietal associative cortex and extended, to variable degrees, to the temporal, occipital and also to the frontal lobes. Hypometabolism was highly asymmetric in four cases. Analysis across the entire group showed a symmetric area of hypometabolism that was confined to the lateral and medial parietal associative cortex.
Conclusion: PCA starts as a presenile and focal syndrome of cerebral atrophy, but tends to develop into generalized dementia. Clinical and imaging data show a high degree of variability. However, PET data show that PCA pathology centers on the parietal lobes and can be correctly addressed as "parietal lobar atrophy". The early presence of memory and the trend towards generalised cognitive decline supports the assumption that many cases are focal variants of Alzheimer's disease. However, cases of Pick's disease with early parietal involvement occur.
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