Abstract
We reported two cases of transcortical sensory aphasia caused by a localized lesion in the deep white matter of the left frontal lobe. The characteristics of language disorders in the two cases were summarized as follows : 1) Spontaneous speech was fluent and paraphasia was observed. 2) Severely impaired auditory comprehension was observed, and echolalia was frequently noted. 3) Repetition was preserved. 4) Reading aloud was preserved but with impaired understanding, revealing a dissociation between reading aloud and comprehension. 5) Moderate to severe impairment of naming and writing letters was observed. From these characteristics, the aphasia type in our cases was considered to be transcortical sensory aphasia.
The lesions of the two cases were found in the deep white matter of the middle frontal gyrus running antero-lateral to the anterior horn of the left lateral ventricle, suggesting the possibility that transcortical sensory aphasia is caused by this lesion. Among individual language disorders that comprise transcortical sensory aphasia, severe impairment of language comprehension poses the most problematic aspect attributable to frontal lobe lesions. SPECT in one case revealed reduced cerebral blood flow in a relatively wide region of the left frontal lobe. Recently it has been reported that impaired comprehension of language is associated with lesions of the middle or lower frontal gyrus. Therefore, it is speculated that impaired comprehension of language results from hypofunction of a relatively wide region of the middle and lower frontal gyri due to a deep white matter lesion of the middle frontal gyrus.
