Implantation of a responsive neurostimulator device in patients with refractory epilepsy

Object. The authors summarize one center's experience with a novel device, the Responsive Neurostimulation (RNS) system, which is used to treat seizures, and they provide technical details regarding the implantation procedure. Methods. The authors reviewed seizure detection, cortical stimulation, and clinical data obtained in 7 patients in whom the RNS system was implanted. Data pertaining to seizure alteration are provided for the first 4 implant-treated patients. The implantation procedure in the case of one patient with occipital lobe heterotopia is included. Results. Based on patients' seizure diaries, the implanted devices functioned at a high sensitivity for clinical seizure detection. Reductions in seizure frequency, based on their diaries and on clinic follow-up notes, ranged from 50 to 75%. No adverse stimulation-induced side effects were noted, and no hardware malfunctions requiring explantation occurred. Generator replacements for battery depletion were required at 11, 17, and 20 months in 3 patients. The implantation procedure was well tolerated, and postoperative hospital stays were short. A revision cranioplasty for a skull defect was performed in the index patient, whose case will be discussed in the most detail. Conclusions. The results obtained in this small preliminary series demonstrate a safe implantation method for the responsive neurostimulation device.