Language after bilateral cerebral infarctions: role of the minor hemisphere in speech.

Language was studied in four patients with bilateral cerebral infarctions. Bilateral destruction of the third frontal gyri did not necessarily produce the severely limited language output characteristic of global or severe Broca aphasia; for Broca aphasia to occur, there must be extensive frontoparietal damage in the dominant cerebral hemisphere. Thus, the marked recovery of language after lesions limited to the dominant third frontal gyrus is mediated by adjacent areas of the dominant hemisphere, and not by the nondominant third frontal gyrus. The nondominant hemisphere nevertheless has a limited capacity to produce oral speech after extensive damage to the dominant hemisphere and may play an appreciable, although still subsidiary, role in normal articulation. The central gyri and rolandic operculum may be more essential than the third frontal gyri for well-articulated speech.