Paroxysmal alien hand syndrome.

Four patients are described who presented with a paroxysmal form of the alien hand syndrome. Two patients with damage to one frontomedial cortex had brief episodes of abnormal motor behaviour of the contralateral arm that featured groping, grasping, and apparently purposeful but perseverative movements, which both patients interpreted as alien or foreign. The other two patients, with posterior parietal damage, reported a paroxysmal feeling of unawareness of the location of the contralateral arm, lack of recognition of the arm as their own, purposeless movements, and personification of the arm. These cases represent a new form of the alien hand syndrome manifested by brief, paroxysmal episodes, which may be due to ictal mechanisms.