[Broca's area and Broca's aphasia: based on the observations of two cases with the lesions involving Broca's area].

Recently, the relation between Broca's area and Broca's aphasia has come into notice again. We investigated two right-handed patients without Broca's aphasia in spite of the presence of lesions involving Broca's area after hemorrhagic infarction. In addition, the clinical findings, the clinical courses and the sites of lesions of two cases were quite similar as follows. They showed no motor deficits and no other abnormal neurological findings from the beginning of the strokes. From the near muteness in the initial stage, speech began to improve gradually. And then, they demonstrated so called transcortical motor aphasia. Namely, repetition and reading aloud were excellent and articulations were normal without phonetic disintegration and dysprosody in contrast to the sparse and limited spontaneous speech. Comprehension was well preserved. Anomia was present and the ability to generate word lists was so poor that, for instance, only two animal names were listed in one minute. Mild to moderate agraphia was present. Agrammatism and buccofacial apraxia were not associated. Afterwards, the two patients showed rapid amelioration. About one month later after the stroke, only a slight difficulty in word finding and mild agraphia remained. In both cases, the lesions confined predominantly to the cortical and subcortical areas in the left posterior part of both the third and the second frontal gyri were confirmed by computerized tomography. According to the evidence from our two cases and to the literature, it may be concluded that the lesion restricted to the posterior part of the third and second frontal gyri in the dominant hemisphere produces a subtype of transcortical motor aphasia and that the lesion restricted to the posterior part of the third frontal gyrus (Broca's area) does not lead to phonetic disintegration.