The phenotypical core of Alzheimer's disease-related and nonrelated variants of the corticobasal syndrome: A systematic clinical, neuropsychological, imaging, and biomarker study

Introduction: The corticobasal syndrome (CBS) constitutes a neurodegenerative disease spectrum with substantial phenotypical or biological heterogeneity, requiring large or multimodal studies to identify its clinico-biological signature while disentangling Alzheimer's disease (AD)-related from non-AD-related CBS. Methods: We analyzed a large (N = 45) monocenter expert-clinic CBS cohort, recruited in motor and/or cognitive units to avoid recruitment biases, assessed with standardized motor and/or cognitive-language tests, brain perfusion imaging, and cerebrospinal fluid biomarkers. Results: CBS mainly manifests as a motor and/or language disorder incorporating a "mixed progressive aphasia" phenotype, consistent with left-lateralized damage to frontal-parietal-temporal cortices. Biomarker expression indicates in 18% underlying AD causing predominant parietal-temporal damage and Gerstmann syndrome (sensitivity 75%; specificity 75%), whereas non-AD-CBS presented with predominant prefrontal and lexical-semantic impairment. Discussion: CBS is primarily a "motor-plus-aphasia" disease unfolding into AD-related and non-AD-related variants with distinctive cognitive-anatomic patterns. CBS, and notably its "Gerstmann variant", should be included in the new AD "lexicon" and categorized in the evolving diagnostic spectrum of "atypical AD" d. (C) 2016 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.