Visualizing language deterioration in progressive aphasias.

摘要

In this issue of Neurology, Gorno-Tempini et al. and Rosen et al. present studies characterizing neuroim-aging and behavioral changes in subtypes of primary progressive aphasia (PPA). They add new information to a large and growing body of literature on the frontotemporal lobar degenerations (FTLD), the second most common cause of dementia in persons under age 65. As this group of illnesses is still less common than other causes of dementia, such as Alzheimer disease (AD) and vascular dementia, both studies were made possible through the systematic study of a large number of such patients performed at a tertiary referral center.In order to explore the anatomic basis for mutism in progressive nonfluent aphasia (PNFA), one form of FTLD, Gorno-Tempini et al. compared gray matter volumes in regions of interest between mute and non-mute patients with PNFA using voxel-based morphometry. Many patients with PNFA eventually develop mutism so it is important to note that patients and controls in this study were matched for disease duration. These investigators found more severe atrophy in the left anterior insula and inferior frontal lobe in persons with PNFA with more prominent atrophy in the pars opercularis and underlying basal ganglia in the subjects with early mutism. This suggests that degeneration of these latter two regions mediates the apraxia of speech underlying the mutism in these patients. Convergent evidence for this association comes from the stroke literature, in which infarction of these regions is most commonly associated with apraxia of speech. It is reassuring that these different approaches toward defining brain-behavior relationships arrive at similar conclusions.