P1‐359: TOPOGRAPHY OF CORTICAL THINNING IN THE LEWY BODY DEMENTIAS

Abstract

Amyloid deposition is common in the Lewy body dementias (LBD), dementia with Lewy bodies (DLB) and Parkinson dementia (PDD), and can be detected with amyloid imaging. We previously showed that cortical thinning on structural MRI in specific cortical regions affected in AD (“AD signature”) can detect AD pathology, even in amyloid-positive asymptomatic subjects. However, the contribution of AD pathology to regional cortical thinning in LBD remains unclear. We hypothesized that the topography of cortical thinning would be similar in DLB and PDD but more severe in DLB, overlapping with the AD signature on the basis of amyloid accumulation, with additional cortical involvement relevant to the distinguishing clinical features of LBD. Thirty-four LBD subjects (19 DLB, 15 PDD) underwent PiB-PET and MRI. PiB DVR with cerebellar gray reference was evaluated to determine amyloid status. DLB (10 amyloid-positive, 9 amyloid-negative) and PDD (7 amyloid-positive, 8 amyloid-negative) subjects underwent vertex-based cortical thickness measurement using Freesurfer v6.0 and were contrasted with a group of 115 aged-matched healthy controls subjects. Results were FDR-adjusted for multiple comparisons (p<0.05). Widespread cortical thinning was observed in DLB, most severe in parietal, lateral and medial temporal regions. In PDD, less severe thinning was evident in an overlapping distribution, greatest in frontal and lateral temporal regions. The distribution of cortical thinning in DLB and PDD overlapped with the AD signature, with additional fusiform, precentral, and posterior cingulate involvement. Cortical thinning was more extensive and severe in amyloid-positive than amyloid-negative DLB subjects, but was evident in both groups in frontal, parietal, lateral and medial temporal regions. The topography of cortical thinning was similar in amyloid-positive DLB and PDD subjects, with greater thinning in DLB that differentially involved medial temporal regions. Cortical thinning was not detected in amyloid-negative PDD. Cortical thinning in LBD overlaps with and extends beyond the AD signature to involve fusiform, precentral, and posterior cingulate regions. Compared to PDD, cortical thinning in DLB is more prominent in lateral and medial temporal regions. The contribution of amyloid deposition to cortical thinning in the LBD is significant and not limited to AD signature regions.