Vagus Nerve Stimulation Improves Seizure Control at 10 Years

Allison Gandey

January 04, 2011

January 4, 2010 — New long-term data show vagus nerve stimulation is a viable option for patients with refractory epilepsy. Presenting at the American Epilepsy Society (AES) 64th Annual Meeting, investigators demonstrated a decade of seizure control.

"Following an initial ramp-up period and accommodation throughout the first year or 2 following implantation, seizure control tended to improve slightly throughout the 10 years of therapy and eventually stabilize," reported the researchers led by Robert Elliott, MD, from New York University Langone Medical Center in New York City.

Seizure frequency was significantly reduced from baseline at each of the recorded intervals (P < .001).

Other centers have shown an improvement in seizure control over time with vagus nerve stimulation. However, the investigators pointed out that most of these studies are prone to methodological biases, such as secondary nonresponder attrition or a declining number of patients.

This study focused on the efficacy of vagus nerve stimulation over time in a series of 65 consecutive patients with focal and generalized treatment-resistant epilepsy who underwent therapy for at least 10 years.

Before vagus nerve stimulation, the mean ± SD weekly seizure frequency was 10.8 ± 24.0 and patients were taking an average of 3 antiepileptic drugs. The mean age of patients was 30 years.

The researchers found that seizure frequency was significantly reduced from baseline at each of the recorded intervals. The mean decrease in seizure frequency at last follow-up was 76.3%.

"This was very clinically effective," Sandra Helmers, MD, from Emory University in Atlanta, Georgia, told Medscape Medical News. Dr. Helmers works with vagus nerve stimulation on a regular basis but was not involved in the current study.

"I use this option a lot," Dr. Helmers said. "Medications often don't cut it for very refractory patients, and I tend to get good results with this. It doesn't work for everybody, but I'm not surprised to see these encouraging 10-year results."

Variation in seizure frequency was common in this population, the researchers add, "and frequent changes in antiepileptic regimens or stimulation parameters were important and possibly synergistic components of seizure control."

It doesn't work for everybody.

In all, 4 patients had intracranial surgery after vagus nerve stimulation. Device removal and reinsertion after craniotomy was required in 2 patients. And another patient had the device removed with a subsequent increase in seizure frequency.

A total of 2 patients died from causes unrelated to epilepsy during the follow-up period. The researchers report no significant difference in number of antiepileptic drugs at any period during follow-up, but changes in regimens were noted at most interval follow-up visits. "Alterations in the device stimulation parameters were common as well," they report, "but less frequent than antiepileptic drug changes."

Dr. Helmers acknowledged this study involved a small number of patients and did not provide any quality-of-life information. Still, she says, she is encouraged by these positive results in very refractory patients.

Welcome Data

Jacqueline French, MD, from New York University's Comprehensive Epilepsy Center in New York City, told Medscape Medical News she welcomes the new long-term data on vagus nerve stimulation but still encourages caution with these approaches. "After a 1-year period," she points out, "about 5% of even severely refractory patients will achieve seizure freedom," even without intervention.

Dr. French is commission cochair of the International League Against Epilepsy Task Force developing a consensus definition of drug-resistant epilepsy.

At last year's AES meeting, Dr. French congratulated the researchers presenting positive results on another investigational neurostimulator known as the RNS System. Unlike continuous stimulation devices already on the market for vagus nerve and deep brain stimulation for Parkinson's disease and essential tremor, the RNS System intervenes in response to detected epileptiform activity.

The results from the RNS System mirrored those of another trial sponsored by Medtronic using a third modality, deep brain stimulation. That study, known as SANTE or Stimulation of the Anterior Nucleus of the Thalamus in Epilepsy, evaluated deep brain stimulation in patients with medically intractable partial epilepsy.

Patient Selection

In a Medscape Experts and Viewpoints, Andrew Wilner, MD, from Lawrence and Memorial Hospital, New London, Connecticut, pointed out that several types of neurostimulation are currently under investigation for epilepsy.

He suggests vagus nerve stimulation be considered for patients in whom 2 to 3 appropriate antiepileptic drugs have failed and are not candidates for resective epilepsy surgery.

"Patients who are good surgical candidates should pursue that route first," he noted, "as complete seizure control is much more likely with resective surgery than with vagus nerve stimulation."

Stimulation may also be considered in patients in whom epilepsy surgery has failed, Dr. Wilner suggests. "Vagus nerve stimulation lacks adverse cognitive side effects, which may prove an advantage in patients who are already receiving one or more antiepileptic drugs."

The researchers have disclosed no relevant financial relationships.

American Epilepsy Society (AES) 64th Annual Meeting: Poster 3.074. Presented December 6, 2010.

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