Literature Review

In epilepsy, brain-responsive stimulation passes long-term tests



Real-world analysis

In the real-world analysis, researchers led by Babak Razavi, PhD, and Casey Halpern, MD, at Stanford University conducted a chart review of 150 patients at eight centers who underwent treatment with the RNS system between 2013 and 2018. All patients were followed at least 1 year, with a mean of 2.3 years. Patients had a median of 7.7 disabling seizures per month. The mean value was 52 and the numbers ranged from 0.1 to 3,000. A total of 60% had abnormal brain MRI findings.

At 1 year, subjects achieved a mean 67% decrease in seizure frequency (interquartile range, 50%-94%). At 2 years, that grew to 77%; at 3 or more years, 84%. There was no significant difference in seizure reduction at 1 year according to age, age at epilepsy onset, duration of epilepsy, location of seizure foci, presence of brain MRI abnormalities, prior intracranial monitoring, prior epilepsy surgery, or prior VNS treatment. When patients who underwent a resection at the time of RNS placement were excluded, the results were similar. There were no significant differences in outcome by center.

A total of 11.3% of patients experienced a device-related serious adverse event, and 4% developed infections. The rate of infection was not significantly different between patients who had the neurostimulator and leads implanted alone (3.0%) and patients who had intracranial EEG diagnostic monitoring (ICM) electrodes removed at the same time (6.1%; P = .38).

Although about one-third of the patients who started the long-term study dropped out before completion, most were because the participants moved away from treatment centers, according to Dr. Morrell, and other evidence points squarely to patient satisfaction. “At the end of the battery’s longevity, the neurostimulator needs to be replaced. It’s an outpatient, 45-minute procedure. Over 90% of patients chose to have it replaced. It’s not the answer for everybody, but the substantial majority of patients choose to continue,” she said.

Extension trial

The open-label extension trial, led by Dileep Nair, MD, of the Cleveland Clinic Foundation and Dr. Morrell, followed 230 of the 256 patients who participated in 2-year phase 3 study or feasibility studies, extending device usage to 9 years. A total of 162 completed follow-up (mean, 7.5 years). The median reduction of seizure frequency was 58% at the end of year 3, and 75% by year 9 (P < .0001; Wilcoxon signed rank). Although patient population enrichment could have explained this observation, other analyses confirmed that the improvement was real.

Nearly 75% had at least a 50% reduction in seizure frequency; 35% had a 90% or greater reduction in seizure frequency. Some patients (18.4%) had at least a full year with no seizures, and 62% who had a 1-year seizure-free period experienced no seizures at the latest follow-up. Overall, 21% had no seizures in the last 6 months of follow-up.

For those with a seizure-free period of more than 1 year, the average duration was 3.2 years (range, 1.04-9.6 years). There was no difference in response among patients based on previous antiseizure medication use or previous epilepsy surgery, VNS treatment, or intracranial monitoring, and there were no differences by patient age at enrollment, age of seizure onset, brain imaging abnormality, seizure onset locality, or number of foci.

The researchers noted improvement in overall Quality of Life in Epilepsy Inventory–89 scores at 1 year (mean, +3.2; P < .0001), which continued through year 9 (mean, +1.9; P < .05). Improvements were also seen in epilepsy targeted (mean, +4.5; P < .001) and cognitive domains (mean, +2.5; P = .005). Risk of infection was 4.1% per procedure, and 12.1% of subjects overall experienced a serious device-related implant infection. Of 35 infections, 16 led to device removal.

The extension study was funded by NeuroPace. NeuroPace supported data entry and institutional review board submission for the real-world trial. Dr. Morrell owns stock and is an employee of NeuroPace. Dr Rao has received support from and/or consulted for NeuroPace.

SOURCE: Nair DR et al. Neurology. 2020 Jul 20. doi: 10.1212/WNL.0000000000010154. Razavi B et al. Epilepsia. 2020 Jul 13. doi: 10.1111/epi.16593.


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