Abstract
A 72-year-old man presented with a 6-month history of decreased voluntary speech. Sparse speech and decreased word fluency were observed. Articulation, naming, comprehension, and repetition were preserved. Agrammatism and paraphasia were not observed. These characteristics matched those reported as dynamic aphasia. Other findings were mild behavioral symptoms, recent memory impairment, and right hemiparkinsonism. The patient's voluntary speech continued to reduce and behavioral symptoms progressed. Brain MRI including voxel-based morphometric analysis showed left-dominant white matter volume reduction in the frontal lobe including those between the left supplementary motor area (SMA)/preSMA and the frontal operculum, likely involving the frontal aslant tract (FAT). The patient became completely mute after two years from disease onset and died of aspiration pneumonia. The neuropathological diagnosis was corticobasal degeneration (CBD). This case suggests that dynamic aphasia may be the initial sign of CBD and that early involvement of left FAT may be responsible for this feature.