Localization of speech parameters by brain scan.

Speech was studied in 18 patients who had a positive radioisotope brain scan within the left hemisphere and a history of a single stroke. Seventeen patients had definite language impariment. In most cases of either fluent or nonfluent aphasia, the center of the scan was behind the central sulcus. Patients with perisylvian involvement were much more likely to have severe comprehension deficit than those without such involvement. Those patients with the most severely decreased fluency were significantly more likely than those more fluent to have markedly decreased comprehension. In an occasional patient, involvement of fluency and comprehension was divergent, suggesting that these processes may be differentially affected.