Innovations in VNS and DBS for Refractory Epilepsy

Aug 06, 2024

Photo Credit: Magicmine

In recent years, there have been various developments in vagal nerve stimulation (VNS) and deep brain stimulation (DBS) modalities to treat patients with refractory epilepsy. Dr. Paul Boon, MD, from Ghent University, Belgium, guided the audience by using the latest research results.

“Over 30% of patients with epilepsy are drug-resistant despite the development of many new anti-seizure medications,” expressed Dr. Boon. VNS and anterior nucleus of the thalamus (ANT)-DBS are two of the options that may help these patients with refractory epilepsy.

Two randomized-controlled trials showed that VNS yields a response rate between 23–31% in patients with refractory epilepsy in the short term, increasing up to 65% over 5 years of follow-up. The side effects of VNS are usually limited. “VNS has positive effects on alertness and mood,” added Dr. Boon. “On the downside, we do not yet know which patients are most likely to respond to VNS, since there are no responder-identification studies available.” In recent years, innovative VNS tools have become available. So-called ‘closed loop VNS’ can detect ictal tachycardia and automatically deliver additional stimulation, resulting in shorter and fewer seizures, with responder rates up to 70%. “The newest tools can even be pre-programmed automatically, reducing the number of visitations of the patients, increasing the ease-of-use, and taking steps towards personalized VNS,” added Dr. Boon. Moreover, last year a study was initiated to assess functional MRI-guided modulation of VNS stimulation parameters. “The preliminary results are promising,” according to Dr. Boon.

ANT-DBS resulted in a 29% greater seizure reduction compared with the control arm in the SANTE trial. The responder rate increased up to 68% after 5 years of follow-up. The MORE study confirmed these findings. “Patients with unifocal epilepsy and no prior epilepsy surgery appeared to respond better to ANT-DBS,” mentioned Dr. Boon. “We also saw a signal of depression and memory impairment with this treatment in the short term.” Furthermore, correct contact positioning and site experience were predictive of improved outcomes. Combining VNS and ANT-DBS may be a promising option for the population as well, a small study (n=33) suggested.

A meta-analysis comparing VNS and ANT-DBS indicated that seizure reduction rates are higher with DBS than with VNS after 1 year (58% vs 33%), a difference that was mostly undone after 3 years (64% vs 54%). A head-to-head comparison of VNS and DBS is unavailable and unlikely to be conducted soon. Finally, VNS is the less expensive option, reducing the cost by approximately 50% as compared with DBS.

“Several novel neurostimulation modalities are emerging, improving the situation for the many patients with drug-resistant epilepsy,” Dr. Boon ended on a positive note.

Medical writing support was provided by Robert van den Heuvel.