Abnormal cortical activation during planning of voluntary movement in patients with epilepsy with focal motor seizures: event-related desynchronization study of electroencephalographic mu rhythm.

Purpose: The spatiotemporal distribution of EEG mu rhythm desynchronization was analyzed in patients with partial epilepsy to determine whether frequent focal motor seizures could induce a change of cortical activation during the planning of a voluntary movement.

Methods: The event-related desynchronization (ERD) of the mu rhythm was quantified during a self-paced voluntary movement of the thumb. The results were compared between two groups of patients with epilepsy: in one group (n = 12), the patients had frontal lobe epilepsy with frequent focal motor seizures (FMS); in the second group (n = 12), they had temporal lobe epilepsy (TLE) with complex partial seizures but no ictal movement disorder. The results were also compared with those of control subjects of same age (n = 10).

Results: In the control group, desynchronization of mu rhythm began over the contralateral central region 2,000 ms before the movement onset. In the FMS group, the desynchronization of mu rhythm was delayed, appearing only 500 ms before the movement onset, and the amplitude of ERD was increased over the frontocentral region. In the TLE group, the spatiotemporal pattern of ERD was the same as in normal subjects, but the amplitude of ERD was increased.

Conclusions: These results indicate that there is a change of reactivity of mu rhythm in patients with partial epilepsy. The change in spatiotemporal pattern of ERD in patients with frequent focal motor seizures suggests that there is an abnormal cortical activation during the planning of a voluntary movement.