Transcortical sensory aphasia following left frontal infarction.

Two right-handed patients who exhibited language disability after left frontal infarction are described. The patients spoke fluently and exhibited excellent repetition ability from the onset of infarction without exhibiting any oral apraxia, but had deficits in auditory comprehension, naming, reading and writing. In both patients, brain magnetic resonance imaging (MRI) revealed infarction in the left inferior frontal gyrus, the middle frontal gyrus and the anterior part of the lower precentral gyrus. Single photon emission computed tomography (SPECT) revealed decreased blood flow in the same regions as those shown to be infarcted by MRI. The MRI and SPECT findings and the symptoms of these patients suggest that left frontal lesions that encompass Broca's area produce fluent aphasia if the posterior part of the left precentral gyrus or motor cortex remains intact and that lesions anterior to Broca's area and the middle frontal gyrus produce a deficit in auditory comprehension of single words as well as sentences.