Abstracts

As part of a multicenter feasibility study, NeuroPace responsive neurostimulators (RNS[trade]) have been implanted in 3 patients with refractory epilepsy. The RNS system (device and leads) is implanted in the skull to continuously monitor and record ECoG from depth or subdural strip electrodes. When electrical seizure discharges are detected, the RNS system delivers electrical stimulation to suppress ictal discharges before a clinical seizure occurs. Subjects (age 18-65) with [gt]=4 disabling, partial seizures/month for 3 consecutive months were implanted with the RNS system. Responsive stimulation was enabled 1 week or later after surgery. Subjects were not blinded to stimulation. Seizure frequency, severity, and adverse events (AEs) were assessed throughout the study. Three adults were implanted with the RNS system. Two had previous invasive EEG monitoring and cortical resection. The RNS device was secured within the right (R) parietal bone in 2 subjects and the left (L) parietal bone in the other. Two 4-electrode subdural strips were connected to each RNS device (Table 1).[table1]Automatic detection of ictal discharges was enabled immediately after surgery. It correctly detected seizures in the 2 subjects that have had seizures since implantation. In both cases seizure onsets were characterized by beta-gamma frequency activity.
Four AEs have been reported, all of which occurred in the first month postop (none during surgery) and all classified as mild. The AEs reported were edema, headache, diarrhea (Subject 1) and possible incision infection (Subject 3). The edema in Subject 1 was further classified as an adverse device effect: post-operative edema around the leads with quick recovery and no sequelae. Product relation was uncertain for one AE: Subject 3 was treated with IV antibiotic for a question of immediate postop wound infection; culture results were negative and the wound healed well. No product complaints have been reported. Among the 3 subjects implanted with the RNS system as of 4/30/04, surgery has been safe. Responsive stimulation has been safe and well tolerated. The device has performed as expected. All AEs have been classified as mild. This is the first report ever of an implanted responsive neurostimulator that continuously monitors ECoG in order to automatically deliver therapy in response to ictal activity. Further implantations are scheduled prior to the Dec 2004 AES meeting. (Supported by NeuroPace)