Innovations in VNS and DBS for refractory epilepsy

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 (Ghent University, Belgium) guided the audience through 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 2 of the options that may help these refractory patients [1].

Two randomised-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% after over 5 years of follow-up [2,3]. 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% [4]. “The newest tools can even be pre-programmed automatically, reducing the number of visitations for the patients, increasing the ease-of-use, and taking steps towards personalised VNS,” added Dr Boon. Moreover, last year a study was initiated to assess functional MRI-guided modulation of VNS stimulation parameters [5]. “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% at 5 years of follow-up [6]. The MORE study confirmed these findings [7]. “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 [8].

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%) [9]. A head-to-head comparison of VNS and DBS is however unavailable and unlikely to be conducted in the near future. Finally, VNS is the less expensive option, reducing the cost by approximately 50% as compared with DBS [10].

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

1. Boon PAJM, et al. Vagal nerve and deep brain stimulation for the treatment of refractory epilepsy. 10th EAN Congress, 29 June–2 July 2024, Helsinki, Finland.
2. Morris GL, et al. Neurology. 1999;53(8):1731-1735.
3. Vonck K, et al. J Clin Neurophysiol. 2004;21(4):283-289.
4. Boon P, et al. Seizure. 2015;32:52-61.
5. Verner R, et al. Front Neurol. 2023;14:1169161.
6. Salanova V, et al. Neurology. 2015;84(10):1017-1025.
7. Peltola J, et al. Neurology. 2023;100(18):e1852-e1865.
8. Parisi V, et al. Neurosurgery. 2021;89(4):686-694.
9. Skrehot HC, et al Epilepsy Behav. 2023;142:109182.
10. Vincent T, et al. J Med Econ. 2022;25(1):1218-1230.

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Posted on 25 July 2024