Hyperventilation and transcranial magnetic stimulation: two methods of activation of epileptiform EEG activity in comparison.

In a prospective study, we compared the established method for an activation of epileptiform activity in EEG, hyperventilation (HV), with the recently presented new activational technique of transcranial magnetic stimulation (TMS) in 10 patients with drug-resistant partial epilepsies. Long-term EEG recordings included subdural electrodes in the course of presurgical evaluation. Epileptiform activity was evaluated visually 500 s before, during, and 500 s after stimulation, and the results were compared statistically. TMS was not better than HV: HV caused an activation of the epileptogenic foci in 6 of 10 cases, TMS only in 3 of 10. Seizures could be induced by HV in 2 of 10, by TMS in no cases. In 2 of 10 cases, TMS even caused a significant reduction of epileptiform activity.