Brief bursts of pulse stimulation terminate afterdischarges caused by cortical stimulation

Objective: To determine whether cortical electrical stimulation can termina te bursts of epileptiform activity in humans, we used afterdischarges (ADs) as a model of epileptiform activity. Methods: Cortical stimulation was per formed for clinical localization purposes using subdural electrodes implant ed in patients undergoing preresection evaluations for treatment of medical ly intractable seizures. We used 0.3-millisecond pulses of alternating pola rity, repeated at 50 pulses/second. When stimulation produced AD, we often applied short additional brief bursts of pulse stimulation (BPS). We examin ed the effectiveness of EPS in aborting ADs in 17 patients using survival a nalysis. Results: With BPS, ADs stopped within 2 seconds in 115 cases, 2 to 5 seconds in 22 cases, and in more than 5 seconds in 89 cases. Without BPS , ADs stopped within 2 seconds in 21 cases, 2 to 5 seconds in 114 cases, an d in more than 5 seconds in 340 cases. BPS was an effective method to abort ADs (Cox proportional hazards model: p < 0.0001). At any time during the c ourse of ADs, the instantaneous rate of stopping ADs within 2 seconds after BPS was applied was 4.6 times greater than when BPS was not applied (95% C I = 3.7, 5.7). In eight cases, ADs progressed to the occurrence of clinical seizures, always when BPS was not applied. Conclusions: Afterdischarges si gnificantly decreased in duration after we applied brief bursts of pulse st imulation. Although afterdischarges are not identical to spontaneous epilep tiform activity, these results support the idea that electrical stimulation , applied in an appropriate manner at seizure onset, could abort seizures i n humans.