Long-term Data Highlight Efficacy of RNS System for Epilepsy

Andrew N. Wilner, MD


February 25, 2019

In November 2013, the RNS System (responsive neurostimulation; NeuroPace, Inc.) was approved by the US Food and Drug Administration (FDA) for the treatment of focal onset refractory epilepsy. Dileep Nair, MD, and Martha Morrell, MD, presented 9-year follow-up data from the long-term treatment trial of the RNS System at the 2018 annual meeting of the American Epilepsy Society in New Orleans, Louisiana.[1]Their results showed that the RNS System led to substantial reductions in seizures, with additional benefits such as improved quality of life, cognition, and memory.

Dr Nair, section head of adult epilepsy and director of intraoperative monitoring at the Cleveland Clinic in Ohio, discussed the findings of this study, the potential benefits of RNS, and where its fits alongside other FDA-approved epilepsy interventions with Medscape reporter Andrew Wilner, MD.

How RNS Works

Wilner: Can you describe the RNS System and how exactly it works?

Nair: The RNS System is a brain-computer interface that treats refractory epilepsy, which affects an estimated 1 million people in the United States alone. It continuously monitors brain activity, recognizing each patient's unique seizure fingerprint, and automatically responds with imperceptible electrical pulses to stop a seizure before it starts. Similar to a pacemaker, the RNS System consists of a small device connected to leads. As a closed-loop, brain-responsive neuromodulation system, it automatically delivers therapy when it detects a specific brain activity pattern that may lead to a seizure.

Physicians can view their patient's brain activity data remotely via a secure website, and can personalize detection and neuromodulation settings to optimize therapy delivery.

Wilner: Which patients with epilepsy can benefit from the RNS System?

Nair: The RNS System is an adjunctive therapy for adults (aged 18+ years) who have frequent, disabling partial-onset (or focal) seizures originating from 1 or 2 epileptogenic foci and are refractory to 2 or more antiepileptic medications.

Wilner: What is your personal experience with the RNS?

Nair: RNS has been a welcome addition to the treatment options for our patients with medically intractable epilepsy.

Some of my patients have reported not just a decrease in number of seizures but also that the seizures they are experiencing become less severe over time. Many patients have found a sense of validation in just being able to see the data generated by the RNS system. They can see the seizures they reported documented in the electrocorticography data, which the RNS systems stores. Often this allows us to make behavioral modification or medication management decisions based on data derived from the RNS system.

Nine-Year Results

Wilner: What were the findings of the 9-year study you recently presented?

Nair: This prospective study evaluated 256 patients across 33 epilepsy centers, with nearly 1900 patient implant-years of follow-up.

Treatment with the RNS System resulted in significant seizure reduction and improved quality of life for patients, including improved memory and cognition. Patients in the study (who had a median baseline of 10 seizures per month) experienced the following outcomes: approximately 3 of 4 patients responded to therapy, achieving at least 50% seizure reduction, with 1 in 3 patients achieving at least 90% seizure reduction; 28% of patients experienced seizure-free periods of 6 months or longer, and 18% experienced seizure-free periods of 1 year or longer; median seizure reduction across all patients was 75% at 9 years; and quality-of-life improvements (including cognition) were sustained through 9 years, with no chronic stimulation-related adverse effects.

Wilner: Which complications of RNS must patients and their physicians be aware of? Does RNS cause psychiatric symptoms?

Nair: Safety outcomes from the clinical trial included no adverse cognitive or neuropsychological effects, no chronic stimulation-related adverse effects, an infection risk of 4.1% per neurostimulator procedure, and a rate of serious device-related adverse events comparable to that of deep brain stimulation (DBS).

The RNS Effect: Sustained Seizure Reduction

Wilner: It seems that seizure control increases with time. Why is that?

Nair: The RNS System provides clinicians with ongoing neural recordings that deliver specific insights into a patient's brain activity, allowing them to personalize and enhance treatment over time. In addition, neuromodulation for the treatment of epilepsy has broadly been shown to improve seizure control over time.

Wilner: Does RNS cure epilepsy? Do any patients become seizure-free?

Nair: Almost a third of patients in the clinical study experienced seizure-free periods of 6 months or longer, and 1 in 3 patients achieved at least 90% seizure reduction. Although the RNS System is not considered a cure for epilepsy, many patients do experience periods of seizure freedom.

Wilner: Because RNS records brain activity for prolonged periods of time, what has it taught us about the electrical activity of the brain and seizure frequency?

Nair: With more than 2.5 million stored electrocorticographic recordings, data from the RNS System are helping advance fundamental research on potential seizure biomarkers, seizure timing and frequency, effects on memory, and possible synergies between specific medications and neuromodulation. No other neuromodulation device has this capability.

Wilner: Where can patients find out whether they are candidates for this therapy?

Nair: Patients can do so by visiting an epilepsy specialist at a comprehensive epilepsy center. Epileptologists at these centers have the expertise to provide patients with a complete evaluation and array of treatment options. Patients can find a center near them by going to the National Association of Epilepsy Centers' website.

Wilner: RNS sounds like a very sophisticated (and expensive) therapy. Is it usually covered by insurance?

Nair: Yes. The RNS System is broadly covered by most public and private insurance.

The State of Neuromodulation for Treating Epilepsy

Wilner: Which other types of neuromodulation might be appropriate for patients who do not respond to medications?

Nair: Other forms of neuromodulation include vagus nerve stimulation and DBS. The RNS System is the only device that records brain activity data that physicians can use to personalize therapy delivery and has no chronic stimulation-related adverse effects.

Wilner: There is an ongoing question of choosing among the 3 types of neuromodulation therapy that are all FDA approved: DBS, RNS, and vagus nerve stimulation. Selim Benbadis, MD, and colleagues recently published an algorithm on the use of epilepsy surgery and neurostimulation.[2] Do you agree with the approach outlined in that paper?

Nair: The approach to determine which type of neuromodulation to use in a specific patient type is an area of active interest in the field. This is something that each level 4 epilepsy center will have to address on an individual basis.

Wilner: As there are now three types of neuromodulation therapy, and perhaps more on the way, such as trigeminal stimulation, do you think there is still a role for epilepsy surgery?

Nair: I believe that epilepsy surgery is still the gold standard treatment in patients with medically intractable focal epilepsy, as long as the epilepsy surgical evaluation shows a high degree of concordance, and if the proposed area of resection is not highly eloquent.

What is clear is that many patients who are medically intractable are not being referred to level 4 epilepsy centers where they can be evaluated. With the advent of these newer therapies, it is my hope that more patients are given the opportunities for better seizure control and better quality of life.

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