Influence of size and site of cerebral lesions on spontaneous recovery of aphasia and on success of language therapy.

Changes in linguistic competence were assessed with the Aachen Aphasia Test in 18 aphasic patients across 8 weeks of spontaneous recovery, 8 weeks of intensive language therapy, and after a follow-up period of 8 weeks without therapy. CT scans were obtained from all patients and were evaluated for size of lesion and for affection of Wernicke's area, adjacent regions of superior and middle temporal gyrus, inferior parietal lesions, and temporobasal lesions. Size of lesion had a negative influence on recovery in all phases. Patients with lesions to temporobasal regions showed less improvement during therapy and less total recovery, but a similar amount of spontaneous recovery than patients without such lesions. Lesions that affected the temporobasal regions were on average larger than those which spared them, but the dissociation between reduced therapy success and unaffected spontaneous recovery became even more conspicuous when the concurrent effect of lesion size was minimized by appropriate selection of patients. Possibly, temporobasal lesions cause a disconnection between the hippocampal formation and perisylvian language areas and hinder explicit learning of linguistic knowledge and compensatory strategies.