The dual effect of vagus nerve stimulation in pediatric patients with drug- resistant epilepsy: Is there more than seizure control?

Abstract Background : Drug-resistant epilepsy (DRE) is very common in our daily clinical practice for which vagal nerve stimulation (VNS) is used as a non-pharmacological therapeutic modality. VNS is offered for patients who are not amenable to resective epilepsy surgery. There is a growing body of evidence suggesting that VNS not only improves seizure control but also modifies cognitive functions. Objective: This study aims at investigating this proposed dual effect as it has a great impact on the developing brain which is crucial, especially in the pediatric age group. Methods: This retrospective-comparative-pilot study was conducted from January 2018 to February 2022 on 2 groups of pediatric patients between the age of 7-18 years with DRE. It included the "VNS group" which underwent VNS implantation after failing at least 3 anti-seizure medications (ASMs) and the "best medical treatment (BMT) group" which received only pharmacological treatment. All included patients were followed up for at least a 12-month period. Demographic data, epilepsy etiology, seizure diary, ASMs, detailed neurological examination, and electroencephalogram (EEG) findings were noted. Cognitive assessment using the Modified Mini-Mental State Examination (MMSE) was recorded and the cognitive score was calculated at baseline and 12 months later for each group. Results: 87.5% of our patients were classified as symptomatic epilepsy. 75% of patients showed ≥50% seizure frequency reduction among the VNS group as compared to 12.5% in the BMT group. None of the patients achieved seizure freedom in both groups. At 12 months, both patients in the BMT and the VNS group showed statistically significant improvement in their overall cognitive score from baseline (p=0.027) and (p=0.012), respectively. However, this improvement was statistically significantly higher in the VNS group as compared to the BMT group (p=0.001). Conclusion : Our preliminary results suggest that VNS might have an added value in ameliorating cognitive impairment and brain maldevelopment in patients with DRE. However, further large-scale prospective long-term studies are still required to explore the potential role of VNS in neuromodulation and neuronal plasticity that might explain such results.