Norwegian population-based study of long-term effects, safety, and predictors of response of vagus nerve stimulation treatment in drug-resistant epilepsy: The NORPulse study.
Kostov KH, Kostov H, Larsson PG, Henning O, Eckmann CAC, Lossius MI, Peltola J.
Epilepsia. 2022 Feb; 63(2): 414-425.
doi: 10.1111/epi.17152.
Vagus nerve stimulation (#VNS) is a viable treatment option for patients with drug resistant epilepsy (#DRE). However, long-term effects studies in a well-defined cohort of patients are sparse in number.
This newly published article by Kostov et al., 2021, aimed to elucidate the efficacy of long-term VNS Therapy in patients with DRE. Furthermore, the study was designed to identify which subset of patients that benefit the most from VNS Therapy.
Highlights
• Effectiveness of VNS Therapy increased over time with a stable antiseizure medication (#ASM) regimen
• Superior responder rates were observed in patients with trauma or stroke induced epilepsies
• Patients with an intellectual disability were less likely to respond to VNS Therapy
The study included 436 DRE patients, 47.2% of the population were children, from a VNS quality registry. For analysis, the patients were divided into three different groups based on VNS response: non-responders (n=181), constant responders (n= 192)or fluctuating responders (n=65). The median #follow-up was 75 months.
The responder rate, expressed as cumulative probability of achieving a ≥50% reduction in seizure frequency, was 58.7% in the overall population at the 5 year follow-up. An early effect of 25%-<50% reduction in seizure burden, 6 months post VNS implantation, was a predictor of response to VNS Therapy (odds ratio: 10.18). The seizure freedom rate was 10.5% after 5 years post VNS implantation.
Noteworthy, patients with a stable ASM regimen achieved significantly higher responder rates. Furthermore, patients with post traumatic or post stroke epilepsies, and patients who were intellectually intact, showed a superior response to VNS Therapy.
The current article suggests the efficacy of VNS Therapy to increase over time with unchanged ASM treatment. Patients with certain epilepsy aetiologies, as well as patients that are intellectually intact, appear to have a superior effect of VNS. This should be taken into consideration during patient selection for VNS Therapy.