Neuropathological investigation of regions responsible for semantic aphasia in frontotemporal lobar degeneration.

Objective: Semantic dementia is a subtype of frontotemporal lobar degeneration, of which an initial symptom is semantic aphasia. Semantic dementia pathologically corresponds to atypical Pick's disease (aPiD), showing ubiq- uitin-positive inclusions similar to those in dementia with motor neuron disease (D-MND). Previous studies have not clarified the regions responsible for semantic aphasia in aPiD, and there have been no reported neuropathological studies concerning its pathomechanism.

Methods: We neuropathologically investigated aPiD and D-MND cases with and without semantic aphasia.

Results: We determined that the regions involved in the early stage of the disease course of semantic dementia were more restricted to the anterior and inferior portion of the temporal lobe on the side of the dominant hemisphere.

Conclusions: Degeneration of the temporal pole is most likely to participate in the pathomechanism of SA in semantic dementia.