Abstracts

The Bereitschaftspotential (BP) is a slow negative potential that precedes voluntary movements. Although very often used in motor control research, its clinical application is scarce. The goal of this study is to present two cases of paroxysmal events in which the BP has been diagnostic in standard video-EEG studies. Two patients presented with sudden jerking of the limbs. A 42-year-old woman had daily abnormal movements of the legs for more than 10 years. They appeared periodically at rest in wakefulness. The second patient is a 55-year-old man with daily sudden jerking of the arms, also in wakefulness, in the last year. The physical exam was normal in both cases. A digital 24-hours video-EEG recording was performed to find at least 100 limb movements. The movement-related potentials were calculated using back-averaging of the EEG activity in relation of jerk onset. In the interictal recordings and during the episodes no epileptiform activity was noted. In the first patient, a BP was found when the patient imitated the movements, but not when studying the actual movements. In the second patient, a clear BP was found when studying the jerking movements. In the first case, the diagnosis of periodic limb movements was established. In the second patient, the voluntary nature of the movement was demonstrated. Back-averaging of movement-related activity is a feasible technique for the diagnosis of paroxysmal events. In the differential diagnosis between seizures, movement disorders and other non-epileptic events, the movement- related potentials can be used as a diagnostic tool if the events are frequent enough.