POSTERIOR CORTICAL ATROPHY IN ALZHEIMERS-DISEASE - ANALYSIS OF A NEW CASE AND REEVALUATION OF A HISTORICAL REPORT

Disturbances of visual function are not uncommon in Alzheimer's diseas e and several cases with complex impairment of visuospatial abilities have been described. For instance, posterior cortical atrophy has been demonstrated in cases displaying Balint's syndrome as the first sympt om of the dementing illness. Such cases showed very high lesion counts in the occipital cortex, as well as in visual association regions in the posterior parietal and posterior cingulate cortex, whereas the pre frontal cortex was consistently less severely involved than usually ob served in Alzheimer's disease. This suggests that the distribution of the lesions had been shifted to specific elements of the visual system . In the present study, we report the quantitative analysis of a new c ase of Alzheimer's disease with possible Balint's syndrome and re-eval uate a case originally described in 1945. The distribution of lesions in these two cases parallels previous observations of Alzheimer's dise ase cases with early visual impairment. Both cases displayed very high densities of neurofibrillary tangles and senile plaques in the primar y visual cortex, secondary visual cortex, visual association areas of the dorsal occipital and posterior parietal lobe and in the posterior cingulate cortex, whereas the prefrontal and inferior temporal regions were comparatively less affected. These cases may define clinical sub groups of Alzheimer's disease and suggest that the breakdown of cortic ocortical projections that is known to occur in dementia may involve s elect components of specific functional systems in certain cases. In p articular, pathways that subserve motion detection and visuospatial an alysis appear to be dramatically affected in these cases presenting wi th Balint's syndrome. Thus, Alzheimer's disease may be a more heteroge neous disorder than previously thought, and refined neuropsychological testing as well as detailed neuropathological evaluation may be of va lue to detect possible clinical variants of this dementing condition.