Closed-loop stimulation in the control of focal epilepsy of insular origin

Background: Previous studies have shown that closed-loop or responsive neurostimulation can abort induced or spontaneous epileptiform discharges. Objective: To assess the effectiveness of a programmable cranially implanted closed-loop neurostimulation system in the control of seizures originating from an area relatively inaccessible by open craniotomy. Method: A patient with drug-resistant partial epilepsy had previously undergone open resection of the left frontal opercular cortex and the underlying insular area. Although subdural-depth electrode ictal recordings had been nonlocalizing, depth electrode insular stimulation had produced the patient's habitual aura. Postoperatively, there was a sustained 50% reduction in seizure frequency. The residual seizures were identical to the preoperative seizures. Repeat depth electrode monitoring revealed that the ictal focus was immediately posterior to the previously resected insular area. A closed-loop cranial internal pulse generator system including left anterior insular and posterior orbitofrontal depth electrodes was implanted. Result: There was an additional 60% reduction of seizures. Conclusion: Preliminary observation indicates that responsive neurostimulation may be an effective alternative to higher-risk resective epilepsy surgery.