Clinical and radiological profile of posterior cortical atrophy and comparison with a group of typical Alzheimer disease and amnestic mild cognitive impairment.

Posterior cortical atrophy (PCA) is a rare dementia affecting higher visual processing and other posterior cortical functions with atrophy and hypometabolism in occipito-parieto-temporal areas, more on right side. The objective of the study was to explore the clinical, neuropsychological, and radiological features of PCA patients and to compare them with typical multi-domain amnestic Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) patients. Four out of 9 patients of PCA fulfilling the criteria of Tang-Wai et al. (2004), 10 patients each of AD and aMCI fulfilling NIA-AA criteria were chosen. Patients were assessed clinically by experienced neurologists. Neuropsychological assessment was performed with standardized validated tests. Each patient underwent an MRI. FDG-PET was done for all PCA and six AD patients. PCA patients were younger, cognitively more impaired with rapid progression showing predominant visuospatial deficits consistent with the damage to the upstream of visual processing. AD patients presented predominantly with amnestic symptoms, with visuospatial dysfunction in some and aMCI had mild memory loss. Marked atrophy and hypometabolism in occipital, parietal and temporal areas in PCA, atrophy and hypometabolism in medial temporal areas in AD and minimal non-localized atrophy in MRI in aMCI were seen. Two PCA patients showed hypometabolism extending to the medial temporal and one to the frontal cortex. The clinical and imaging features of PCA are consistent with the damage predominantly to the upstream of visual processing. The difference between PCA and typical AD suggests involvement of AD pathology at different sites within a common disease-relevant network of brain regions.