Lobar Microbleeds in the Posterior Cortical Atrophy Syndrome: A Comparison to Typical Alzheimer's Disease.

PURPOSE OF THE STUDY: Posterior cortical atrophy is a clinico-radiographical syndrome that presents with higher-order visual dysfunction and is most commonly due to Alzheimer's disease. Understanding factors associated with atypical presentations of Alzheimer's disease, such as posterior cortical atrophy (PCA), holds promise to shape our understanding of AD pathophysiology. Thus, we aimed to compare MRI evidence of lobar microbleeds (LMBs) in posterior cortical atrophy (PCA) syndrome to typical AD (tAD) and to assess and compare MRI evidence of cerebral amyloid angiopathy (CAA) in each group. FINDINGS: We retrospectively collected clinical and MRI data from participants with PCA (n = 26), identified from an institutional PCA registry, and participants with tAD (n = 46) identified from electronic health records from a single institution. LMBs were identified on susceptibility-weighted imaging (SWI); the Fazekas grade of white matter disease was assessed using FLAIR images, and Boston criteria version 2.0 for cerebral amyloid angiopathy were applied to all data. The proportion of participants with PCA and LMB (7.7%) was lower than for tAD (47.8%) (p = 0.005). The frequency of "probable" CAA was similar in both groups, while "possible" CAA was more frequent in tAD (30.4%) than PCA (0%) (p = 0.001). The Fazekas grades were not different between groups. Lobar microbleeds on SWI were not more common in PCA than in typical AD. Clinicopathological investigations are necessary to confirm these findings. The factors that contribute to the posterior cortical atrophy phenotype are unknown.

Perspectives and a Systematic Scoping Review on Longitudinal Profiles of Posterior Cortical Atrophy Syndrome.

PURPOSE OF REVIEW: To provide perspectives on the importance of understanding longitudinal profiles of posterior cortical atrophy (PCA) and report results of a scoping review to identify data and knowledge gaps related to PCA survival and longitudinal clinical and biomarker outcomes. RECENT FINDINGS: Thirteen longitudinal studies were identified; all but two had fewer than 30 participants with PCA. Relatively few longitudinal data exist, particularly for survival. In PCA, posterior cortical dysfunction and atrophy progress at faster rates compared to non-posterior regions, potentially up to a decade after symptom onset. Unlike typical AD, PCA phenotype-defined cognitive dysfunction and atrophy remain relatively more severe compared to other regions throughout the PCA course. Select cognitive tests hold promise as PCA outcome measures and for staging. Further longitudinal investigations are critically needed to enable PCA inclusion in treatment trials and to provide appropriate care to patients and enhance our understanding of the pathophysiology of dementing diseases.