Apraxia and the Supplementary Motor Area

Anatomical, electrophysiological, and cerebral blood flow studies suggest that the supplementary motor area (SMA) may be important for programming certain skilled motor acts of the limbs. However, to our knowledge, abnormalities of complex distal motor behavior following SMA lesions have not been reported. We have studied two patients with left mesial hemisphere infarctions that included the SMA. These patients had bilateral ideomotor apraxia for transitive limb movements without buccofacial apraxia. The observations suggest that the types of skilled motor acts programmed by the left SMA are learned transitive limb movements.