RNS offers hope for patients with drug-resistant epilepsy as surgery alternative, study shows

For many living with epilepsy, medication is effective. “However, a third of patients with epilepsy are refractory to medications,” explains Dawn S. Eliashiv, MD, professor of neurology and co-director of the UCLA Seizure Disorder Center. “That means they didn’t respond to two medications and still have seizures.”

Historically, the next step involved surgery to remove the brain tissue generating seizures. But surgery is not always possible and may carry neurological risks. A newer approach, responsive neurostimulation (RNS), allows clinicians to control seizures through technology without removing brain tissue, offering hope to patients who are not candidates for surgical resection.

Listening to the brain

RNS is a form of neuromodulation designed to detect and interrupt seizure activity at its earliest stages. The NeuroPace RNS System was FDA approved in the United States in 2013 for treating patients whose seizures do not respond to medication.  In the procedure, physicians implant a small neurostimulator beneath the skull. Thin electrodes are placed in or near the areas of the brain where seizures originate, either deep within brain structures or positioned on the surface of the brain. The device then acts as an internal observer.

“It has the ability to record brain waves directly from those structures,” Dr. Eliashiv explains. “Using algorithms that recognize the electrical patterns specific to that patient’s seizures, the device can detect when a seizure
is beginning.”

When those patterns appear, the system responds instantly by delivering brief electrical pulses through the electrodes. The stimulation may halt the seizure almost immediately. Over time, however, neurologists believe this therapy does something even more interesting.

“It can stop seizures in some cases,” Dr. Eliashiv says, “but what we’ve learned is that it also modulates brain activity and decreases the tendency to have seizures over time.”

The value of RNS becomes particularly clear when seizures originate in regions of the brain that surgeons cannot safely resect. A recent study led by UCLA investigators, published in Seizure: European Journal of Epilepsy, assessed the 20 patients with drug-resistant focal motor epilepsy who received RNS in the primary motor cortex. For these patients, traditional epilepsy resection surgery carried a risk of profound motor deficits.

The study offered encouraging results. About half of the patients experienced greater than 90% reduction in seizure frequency. Just as important, the treatment offered a therapeutic pathway where none previously existed.

RNS therapy: A growing field

Even when epilepsy surgery is technically possible, it can carry neurological trade-offs depending on the region of the brain involved.

“In the past, we might perform resections of the dominant temporal lobe,” Dr. Eliashiv notes. “Patients could have a good seizure outcome but then develop memory deficits or cognitive problems.”

RNS offers a more conservative alternative. Rather than removing brain tissue, physicians implant electrodes and monitor brain activity while providing responsive stimulation.

RNS also provides diagnostic advantages when physicians are uncertain which side of the brain generates seizures, as the device can monitor both regions simultaneously.

“With RNS, we can implant electrodes on both temporal lobes and monitor over a long period of time,” Dr. Eliashiv says. “We can see where the seizures are actually coming from while also delivering therapy.”

This dual-role treatment, combined with long-term brain monitoring, is one of the system’s unique strengths.

RNS belongs to a family of neuromodulation therapies for epilepsy, alongside vagus nerve stimulation, which stimulates the vagus nerve in the neck, and deep brain stimulation targeting structures within the thalamus. However, RNS differs in one critical respect: it is responsive rather than continuous.

“This device looks at brain patterns, recognizes the seizure pattern, and then delivers a response,” Dr. Eliashiv explains. “That responsive quality is unique.”

Researchers are also exploring whether expanding the system’s targets might allow it to treat broader forms of epilepsy, including some generalized seizure disorders.

Looking Forward

The emergence of RNS reflects a broader shift toward individualized, data-driven treatments that adapt to each patient’s brain. This shift carries enormous implications, as approximately 1.4 million people live with drug-resistant epilepsy in the U.S. alone.

“The big takeaway,” says Dr. Eliashiv, “is to consider, for patients with refractory epilepsy, more options that include neuromodulation in general and RNS specifically.”

Researchers are actively investigating new targets in the brain, more sophisticated algorithms for detecting seizure activity, and broader neurological applications. For now, RNS offers meaningful control to epilepsy patients who once had very few treatment options.

For more information, please visit https://www.uclahealth.org/international-services/ or call +1 310-794-8759