[Callosal disconnection syndrome caused by left hemisphere infarction].

A 49-year old right-handed taxi-driver experienced right upper limb weakness and global aphasia following internal carotid artery occlusion. Five months later, aphasia and hemiparesis had resolved but he complained of difficulties in his daily activities, termed "inner conflict". Specific testings disclosed typical features of a callosal syndrome: left unilateral ideomotor apraxia, left hand agraphia, left tactile dysnomia, right hand constructional difficulties, and left ear extinction on dichotic listening. Naming and recognition of tachistoscopically presented images or words was similar to that of classical split-brain studies. MRI showed a left-hemisphere periventricular increased signal involving the callosal outflow of the whole posterior half of the corpus callosum and partially destroying the splenium. Fibers from the anterior half of the body and the genu were spared. According to clinical and MRI findings in this case and other documented cases of callosal syndrome, localization of callosal transfer of various hemisphere functions is discussed. The relevance of callosal symptoms to the diagnosis of watershed infarcts is emphasized.