Amyloid imaging in atypical presentations of Alzheimer's disease.

Alzheimer's disease (AD) is thought to progress in a fairly stereotyped manner, with episodic memory loss being the first and most salient domain of impairment, reflecting the early disease in structures supporting this function. However, there is considerable heterogeneity in the relative involvement of different cognitive domains, and at the extreme are three syndromes associated with AD: (1) logopenic progressive aphasia, (2) posterior cortical atrophy, and (3) frontal variant of AD. As each of these syndromes is variably associated with non-AD dementia and clinically overlaps with other presentations more commonly associated with different causes of neurodegeneration (e.g., progressive nonfluent aphasia), the use of amyloid imaging for detection of the molecular pathologic features of AD is of significant clinical value. This article reviews several amyloid imaging studies of these populations which support autopsy case series and reveal a dissociation between the spatial distribution of amyloid plaques and clinical phenotype.