[A case of bilingual aphasia with language mixing between Japanese and English caused by superior longitudinal fasciculus lesion-a study using functional MRI and diffusion tensor imaging].

We report a case of left-handed bilingual aphasia with phonemic paraphasia and language mixing from Japanese as a first language to English as a second language. The lesion caused by cerebral infarction was mainly localized in the left parietal lobe white matter. The patient was a 46-year-old, left-handed woman who was bilingual in Japanese and English. Both auditory and visual comprehensions were well maintained after the acute phase of the disease; however, language mixing between Japanese and English was observed during Japanese speech. A pathophysiological interpretation of this case required a focus on the brain network. Our findings suggest that lesions of the superior longitudinal fasciculus and arcuate fasciculus of the white matter fibers just below the left inferior parietal lobule are associated with bilingual aphasia.