Responsive Stimulation May Be Viable Treatment for Medically Intractable Mesial Temporal Lobe Epilepsy

VANCOUVER, British Columbia — Researchers from Houston, Texas, and Mountain View, California, have found that responsive stimulation may be a viable treatment option for patients with medically intractable mesial temporal lobe epilepsy (MTLE). The researchers presented their findings at the 68^th annual meeting of the American Academy of Neurology (AAN).

“Temporal lobectomy is the best treatment option for many patients with medically intractable unilateral mesial temporal lobe epilepsy. However, some patients fail to respond or have bilateral independent onsets. For others, surgery carries an unacceptable risk for neurologic morbidity,” wrote Paul Van Ness, MD, FACNS, from the Department of Neurology at the Baylor College of Medicine and director of the Baylor Comprehensive Epilepsy Center in Houston, and colleagues. “These MTLE patients may be candidates for responsive neurostimulation.”

The researchers identified participants from those who were enrolled in clinical trials of a responsive neurostimulator (RNS® System, NeuroPace). They identified 111 participants with MTLE whose seizures arose solely from the mesial temporal lobe. The average age at enrollment was 37.3 years, and the median baseline seizure frequency was 7.7 per month (range, 3 to 217). Of the 111 participants, 72% (n=80) had bilateral onsets and 28% (n=31) had unilateral onsets.

The participants were implanted with an average of 2.3 leads; 76 participants had depth leads only, 29 participants had both depth and strip leads, and 6 participants had only strip leads. Mean follow-up time was 6.1 years (range: 5 weeks to 10.4 years). In patients with valid seizure diary data, the percentage change in clinical seizure frequency was calculated by comparing the most recent 3 months of data in the open-label period to the pre-implant baseline period (last observation carried forward [LOCF]).

The LOCF analysis of 106 participants showed a median percentage reduction of seizures of 70%. Serious device-related adverse events occurred in at least 2.5% of the MTLE subjects over the 671 implant years; these included device lead damage in 7 subjects, soft tissue implant site infection in 13 subjects, and an infection rate of 3.6% per neurostimulator procedure. There were no adverse neuropsychologic or mood effects.

“We expected to see a benefit but were unsure how much of an impact the RNS system would have. We were happy to see that some patients were seizure free, since that was uncommon in prior neurostimulation device studies and with pharmaceutical studies,” Dr Van Ness told Neurology Advisor. “These results show that selected patients can benefit from RNS, even when [treatment with] medications, epilepsy resections, and the vagus nerve stimulator [failed]. If a patient has intractable focal epilepsy, they should be evaluated at an epilepsy center to see if they are a candidate for epilepsy surgery or a device implant.”

Dr Van Ness added that while the patients in this study have had many years of follow-up, more would be even better in future research. “Epilepsy has many etiologies and can present in many ways.  Research into new stimulation and detection protocols may improve results further for specific subsets of patients,” he said. Possible aspects to test further in the future could include whether additional recording or stimulating electrodes would be helpful for larger epileptogenic zones, and whether children could benefit from the device. Dr Van Ness also noted that the RNS device may become more sophisticated with longer- lasting batteries or a rechargeable battery.

“The RNS pivotal trial patients should be commended for participating in this challenging study,” said Dr Van Ness. “The idea of willingly implanting an experimental device in one’s head shows how seriously these patients are affected by epilepsy. I hope that patients, families, and physicians recognize that there is hope for those [for whom] everything else that came previously [failed].”

Disclosures: P. Van Ness: NeuroPace, JAMA Neurology editorial board. T. Crowder Skarpaas: NeuroPace, NeuroPace. M. Morrell: NeuroPace.

Click here for more coverage from the 68^th Annual Meeting of the American Academy of Neurology, April 15-21, 2016, in Vancouver, British Columbia, Canada.

Reference

Van Ness P, Skarpaas TC, Morrell M; The RNS System Investigators. Long-term outcome of adults with medically intractable mesial temporal lobe seizures treated with responsive neurostimulation. Presented at: The 68^th Annual Meeting of the American Academy of Neurology. April 15-21, 2016; Vancouver, British Columbia, Canada. Presentation I8.009.