[A case of corticobasal degeneration presenting with primary progressive aphasia]

We report a 64-year-old right-handed woman whose initial symptom was slowly progressive aphasia without generalized dementia and who was subsequently diagnosed as having corticobasal degeneration (CBD). Neurological examination revealed disturbed vertical gaze, dysarthria, rigidity of the right upper extremity, and bilateral instinctive grasp reaction. Neuropsychological assessment disclosed Broca's aphasia, buccofacial apraxia, and memory disturbance. MRI of the brain showed atrophy of the frontotemporal lobes, which was more severe on the left than on the right, especially the left inferior frontal gyrus. In most reported cases of CBD, the initial symptom is motor dysfunction of the unilateral upper or lower extremity. However, we should be cautious that among cases with CBD, there have been rare cases that begin with progressive aphasia alone. In our case, the atrophied region of the cerebral cortex was most severe around the left inferior frontal gyrus. In a few reported cases with the initial symptom of aphasia, the atrophied region corresponded considerably to the type of the aphasia. On the other hand, in those whose initial symptom was mainly motor dysfunction of the unilateral extremity, the atrophied region was remarkable in the posterior part of the frontal lobe and parietal lobe. Therefore, we suggest that in CBD the distribution of the cerebral cortical lesions differs in accordance with whether the initial symptom is motor disturbance or aphasia, and that the type of aphasia corresponds to the location of the cortical lesion.