Negative potential shifts and the prediction of the outcome of neurofeedback therapy in epilepsy.

About two-thirds of epilepsy patients who learn to control their slow cortical potential shifts (SCP) reduce their seizure rate, but the remaining third does not demonstrate clinical improvement. In the present study, this finding was replicated in a group of 27 patients with focal epilepsy. We found that patients who consistently produced larger negative SCP in all conditions during the first phase of treatment, showed no decrease in seizure frequency during the six-month follow-up, as compared with the three-month baseline phase. The large negative SCP explained about one-third of the variance of the clinical outcome. Age, medication, seizure history, or the localization of focus were found to be unrelated to clinical improvement.