Callosal apraxia.

A 43-year-old woman suffered a spontaneous corpus callosum disconnection, resulting in apraxia and apraxic agraphia confined to the left hand. She initially had a functionally total callosal disconnection. With time, the splenium of the corpus callosum became functional, and a computerized tomographic scan performed five months after the onset showed infarction of only the body of the corpus callosum. Concomitant with this improvement in callosal function, the apraxia changed from ideational (loss of the concept of skilled movements) to classic ideomotor apraxia. A temporal analysis of this case provided support for Liepmann's (Liepmann, 1900; Liepmann and Maas, 1970) hypothesis that there is a centre for visuokinaesthetic (space-time) engrams in the left hemisphere of right-handed patients that controls skilled motor acts in either hand. This patient's recovery also allowed us a better understanding of the mechanisms underlying various types of apraxia.