Longitudinal changes in grey matter volumes and cortical thickness in Posterior Cortical Atrophy

Abstract

Posterior Cortical Atrophy (PCA) is a form of dementia most commonly associated with Alzheimer's disease (AD) pathology. Cross-sectional imaging studies have shown different atrophy patterns in PCA compared with typical (amnestic) AD (tAD), with PCA showing tissue loss predominantly in parietal regions and tAD mostly in temporal lobe regions. However, changes in grey matter volume and cortical thickness over time are not well understood, particularly in PCA. This study assessed longitudinal changes in grey matter volume and cortical thickness in PCA, tAD and controls. The study included 18 PCA and 16 tAD patients, and 18 healthy controls (Table). Two volumetric MRI scans (approximately one year interval) were included per subject. Changes in grey matter volume were measured using nonlinear-registration and voxel-based morphometry (VBM, in SPM8), and cortical thickness changes were measured using FreeSurfer (v4.5.0). Changes were regressed against interval, age and gender. Statistical significance of the group differences was tested using a multiple-comparison correction (FDR) at p = 0.05. Figure A shows raw differences in grey matter volume change between controls and PCA (left), controls and tAD (middle) and PCA and tAD (right). Both PCA and tAD show global loss in grey matter compared with controls throughout the cortex, with the greatest (and statistically significant) differences in temporal and parietal lobe regions. The direct comparison of PCA and tAD shows non-significant trends towards greater grey matter loss in superior frontal regions in PCA compared with tAD, and anterior temporal and anterior frontal regions in tAD compared with PCA. Similar results were obtained by the cortical thickness analyses, presented as raw differences in Figure B. The direct disease-group comparison showed non-significant trends towards greater differences in inferior parietal and medial frontal regions in PCA compared with tAD, and greater differences in temporal and posterior parietal regions in tAD compared with PCA.