Literature Review

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



Two new long-term studies, one an extension trial and the other an analysis of real-world experience, show that the RNS System direct brain responsive neurostimulator leads to reduction of seizure frequency in most epilepsy patients who had it implanted. Both studies showed that the benefit from the devices increased over time.

That accruing benefit may be because of improved protocols as clinicians gain experience with the device or because of network remodeling that occurs over time as seizures are controlled. “I think it’s both,” said Martha Morrell, MD, a clinical professor of neurology at Stanford (Calif.) University and chief medical officer at NeuroPace, the company that has marketed the device since it gained FDA approval in 2013.

In both studies, the slope of improvement over time was similar, but the real-world study showed greater improvement at the beginning of treatment. “I think the slopes represent physiological changes, but the fact that [the real-world study] starts with better outcomes is, I think, directly attributable to learning. When the long-term study was started in 2004, this had never been done before, and we had to make a highly educated guess about what we should do, and the initial stimulatory parameters were programmed in a way that’s very similar to what was used for movement disorders,” Dr. Morrell said in an interview.

The long-term treatment study appeared online July 20 in the journal Neurology, while the real-world analysis was published July 13 in Epilepsia.

An alternative option

Medications can effectively treat some seizures, but 30%-40% of patients must turn to other options for control. Surgery can sometimes be curative, but is not suitable for some patients. Other stimulation devices include vagus nerve stimulation (VNS), which sends pulses from a chest implant to the vagus nerve, reducing epileptic attacks through an unknown mechanism. Deep brain stimulation (DBS) places electrodes that deliver stimulation to the anterior nucleus of the thalamus, which can spread initially localized seizures.

The RNS device consists of a neurostimulator implanted cranially and connected to leads that are placed based on the individual patient’s seizure focus or foci. It also continuously monitors brain activity and delivers stimulation only when its signal suggests the beginning of a seizure.

That capacity for recording is a key benefit because the information can be stored and analyzed, according to Vikram Rao, MD, PhD, a coinvestigator in the real-world trial and an associate professor and the epilepsy division chief at the University of California, San Francisco, which was one of the trial centers. “You know more precisely than we previously did how many seizures a patient is having. Many of our patients are not able to quantify their seizures with perfect accuracy, so we’re better quantifying their seizure burden,” Dr. Rao said in an interview.

The ability to monitor patients can also improve clinical management. Dr. Morrell recounted an elderly patient who for many years has driven 5 hours for appointments. Recently she was able to review his data from the RNS System remotely. She determined that he was doing fine and, after a telephone consultation, told him he didn’t need to come in for a scheduled visit.


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