Preservation of Memory in Alzheimer-Related Primary Progressive Aphasia Glass Half Full

摘要

Primary progressive aphasia (PPA) denotes gradual deterioration of language function due to neurodegeneration. Although PPA was initially considered 1 of the 2 main clinical syndromes of frontotemporal dementia pathologies, we now know that about one-third of all PPA cases are due to underlying Alzheimer disease (AD) pathology. Over the past quarter-century, the main focus of PPA research has been on phenotyping and differentiating its related language disorders and on the significant clinical and pathologic heterogeneity of the syndrome. A very important but less considered aspect, however, is the remarkable preservation of another aspect of cognition, namely memory, in this condition. This is especially relevant in the case of Alzheimer-related PPA (PPA-AD), given that AD pathology is often considered synonymous with the presence of memory problems. In this issue of Neurology?, Mesulam et al.2 elegantly tackle the issue of resilience of memory function in PPA-AD. In a longitudinal follow-up of a cohort of 31 patients with AD divided between typical amnestic and language presentations, the authors examined a number of important issues. First, comparison of the neuropsychological profiles of the 2 groups indicated that the typical AD group had as much naming deficit as the PPA-AD group, suggesting that the main difference between the 2 groups was in preservation of memory rather than involvement of language. Second, the authors found that the 2 groups had comparable degrees of AD pathology in the medial temporal lobe (all 14 of the patients with typical AD and 8 of the 17 patients with PPA-AD had had an autopsy).