Degenerative and Vascular Fluent Aphasia: Looking for Differences

Objective: To investigate whether the characteristics of language disorders of degenerative and vascular aphasias depend on the underlying neuropathology. Methods: Logopenic variant/mixed primary progressive aphasics (lvmPPA; n=18) and poststroke fluent aphasics (PSA; n=11) underwent a neuropsychological examination and an assessment of the macro- and microlinguistic aspects of language. A principal component analysis and a cluster analysis applying a two-group solution were performed on the scores obtained from the neuropsychological and language examination. Results: Global cognition, lexical-semantic, and morphosyntactic components, and two components loading macrolinguistic variables, were extracted by the principal component analysis. A first cluster of 18 participants (14 lvmPPA and 4 PSA) and a second cluster of 11 participants (4 lvmPPA and 7 PSA) were identified. Participants in the first cluster were significantly more impaired than those in the second cluster in global cognition, lexical-semantic, and morphosyntactic components. Macrolinguistic components did not differentiate the two clusters. lvmPPA in the first cluster showed bilateral cortical thinning (greater on the left), whereas lvmPPA in the second cluster showed atrophy only in the left. Participants with PSA in both clusters showed vascular lesions encompassing the posterior left perisylvian regions. Underestimation of the severity of the leukoencephalopathy and damage of the interhemispheric connectivity might be responsible for the inclusion of PSA individuals in the first cluster, despite a unilateral lesion. Conclusions: Lesion localization is the main factor that determines the characteristics of aphasic deficits. Etiology indirectly acts through a different sensitivity of the brain regions to various pathologies.