Ness, Paul C. Van

SummaryObjectiveEvaluate the seizure‐reduction response and safety of mesial temporal lobe (MTL) brain‐responsive stimulation in adults with medically intractable partial‐onset seizures of mesial temporal lobe origin.MethodsSubjects with mesial temporal lobe epilepsy (MTLE) were identified from prospective clinical trials of a brain‐responsive neurostimulator (RNS System, NeuroPace). The seizure reduction over years 2–6 postimplantation was calculated by assessing the seizure frequency compared to a preimplantation baseline. Safety was assessed based on reported adverse events.ResultsThere were 111 subjects with MTLE; 72% of subjects had bilateral MTL onsets and 28% had unilateral onsets. Subjects had one to four leads placed; only two leads could be connected to the device. Seventy‐six subjects had depth leads only, 29 had both depth and strip leads, and 6 had only strip leads. The mean follow‐up was 6.1 ± (standard deviation) 2.2 years. The median percent seizure reduction was 70% (last observation carried forward). Twenty‐nine percent of subjects experienced at least one seizure‐free period of 6 months or longer, and 15% experienced at least one seizure‐free period of 1 year or longer. There was no difference in seizure reduction in subjects with and without mesial temporal sclerosis (MTS), bilateral MTL onsets, prior resection, prior intracranial monitoring, and prior vagus nerve stimulation. In addition, seizure reduction was not dependent on the location of depth leads relative to the hippocampus. The most frequent serious device‐related adverse event was soft tissue implant‐site infection (overall rate, including events categorized as device‐related, uncertain, or not device‐related: 0.03 per implant year, which is not greater than with other neurostimulation devices).SignificanceBrain‐responsive stimulation represents a safe and effective treatment option for patients with medically intractable epilepsy, including patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior MTL resection.

Summary Objective Patients with suspected mesial temporal lobe ( MTL ) epilepsy typically undergo inpatient video–electroencephalography ( EEG ) monitoring with scalp and/or intracranial electrodes for 1 to 2 weeks to localize and lateralize the seizure focus or foci. Chronic ambulatory electrocorticography ( EC oG) in patients with MTL epilepsy may provide additional information about seizure lateralization. This analysis describes data obtained from chronic ambulatory EC oG in patients with suspected bilateral MTL epilepsy in order to assess the time required to determine the seizure lateralization and whether this information could influence treatment decisions. Methods Ambulatory EC oG was reviewed in patients with suspected bilateral MTL epilepsy who were among a larger cohort with intractable epilepsy participating in a randomized controlled trial of responsive neurostimulation. Subjects were implanted with bilateral MTL leads and a cranially implanted neurostimulator programmed to detect abnormal interictal and ictal EC oG activity. EC oG data stored by the neurostimulator were reviewed to determine the lateralization of electrographic seizures and the interval of time until independent bilateral MTL electrographic seizures were recorded. Results Eighty‐two subjects were implanted with bilateral MTL leads and followed for 4.7 years on average (median 4.9 years). Independent bilateral MTL electrographic seizures were recorded in 84%. The average time to record bilateral electrographic seizures in the ambulatory setting was 41.6 days (median 13 days, range 0–376 days). Sixteen percent had only unilateral electrographic seizures after an average of 4.6 years of recording. Significance About one third of the subjects implanted with bilateral MTL electrodes required >1 month of chronic ambulatory EC oG before the first contralateral MTL electrographic seizure was recorded. Some patients with suspected bilateral MTL seizures had only unilateral electrographic seizures. Chronic ambulatory EC oG in patients with suspected bilateral MTL seizures provides data in a naturalistic setting, may complement data from inpatient video‐ EEG monitoring, and can contribute to treatment decisions.

Summary Objective To demonstrate the safety and effectiveness of responsive stimulation at the seizure focus as an adjunctive therapy to reduce the frequency of seizures in adults with medically intractable partial onset seizures arising from one or two seizure foci. Methods Randomized multicenter double‐blinded controlled trial of responsive focal cortical stimulation (RNS System). Subjects with medically intractable partial onset seizures from one or two foci were implanted, and 1 month postimplant were randomized 1:1 to active or sham stimulation. After the fifth postimplant month, all subjects received responsive stimulation in an open label period ( OLP ) to complete 2 years of postimplant follow‐up. Results All 191 subjects were randomized. The percent change in seizures at the end of the blinded period was −37.9% in the active and −17.3% in the sham stimulation group (p = 0.012, Generalized Estimating Equations). The median percent reduction in seizures in the OLP was 44% at 1 year and 53% at 2 years, which represents a progressive and significant improvement with time (p < 0.0001). The serious adverse event rate was not different between subjects receiving active and sham stimulation. Adverse events were consistent with the known risks of an implanted medical device, seizures, and of other epilepsy treatments. There were no adverse effects on neuropsychological function or mood. Significance Responsive stimulation to the seizure focus reduced the frequency of partial‐onset seizures acutely, showed improving seizure reduction over time, was well tolerated, and was acceptably safe. The RNS System provides an additional treatment option for patients with medically intractable partial‐onset seizures.