Aphasia following Non-Haemorrhagic Lesions in the Left Striato-Capsular Region

Eleven subjects exhibiting language pathology following non-haemorrhagic, striato-capsular lesions in the left hemisphere were investigated with the Boston Diagnostic Aphasia Examination at least six months post-onset of their neurological deficit. C.T. scans were obtained from all subjects and their lesions mapped onto standardized cross-sectional model diagrams of the human brain. Those subjects with lesions involving the anterior limb of the internal capsule, the head of the caudate nucleus and/or the anterior portion of the putamen exhibited an atypical, non-fluent aphasia which could not readily be classified in terms of the classic cortical aphasia syndrome. Posterior striato-capsular lesions centered on the posterior limb of the internal capsule and neighbouring basal ganglia were associated with a fluent, Wernicke's-like aphasia. Lesions which included both anterior and posterior striato-capsular structures in most cases produced a global aphasia. The results are discussed in terms of a recent theory of the participation of the dominant striatum and internal capsule in language processing.