Efficacy of vagus nerve stimulation (VNS) in refractory Dravet syndrome: a case report

Abstract

Case Presentation: A 3-year-old male patient, D.C.G., diagnosed with DS and experiencing seizures since 2 months of age. In May 2024, he presented with difficult-to-control epilepsy, suffering up to 7 seizures per day despite the use of five antiepileptic drugs (Valproate, Lamotrigine, Clobazam, Oxcarbazepine, and Topiramate). EEG showed a left frontotemporal epileptiform disorder and brain MRI already demonstrated signs of mesial temporal sclerosis. Given the refractory condition, VNS implantation was indicated. After serial adjustments of the device since July 2024 (current parameters at 1.5mA), the patient showed significant improvement in seizure frequency, currently experiencing 1 seizure every two months. This outcome represents a reduction greater than 90%, meeting the "responder" criterion (reduction > 50%). Furthermore, this clinical improvement allowed for the withdrawal and adjustment of medications. Discussion: The meta-analysis by Chen et al. (2024), which included 16 studies and 197 patients, demonstrated an overall VNS efficacy rate of 54% in DS. Literature suggests that VNS efficacy increases significantly within the first 6 months of treatment, and early implantation may foster benign neural network changes and prevent irreversible damage caused by prolonged and frequent seizures. Beyond ictal control, VNS use in DS has been associated with subjective gains in attention and language across several studies. Final Comments: Vagus nerve stimulation can, therefore, be a viable and highly effective therapeutic option for patients with DS. VNS provides not only a reduction in seizure frequency but also pharmacological tapering, along with cognitive and behavioral improvements. VNS should be considered early when drug resistance is established, thereby improving the prognosis and quality of life of children with refractory epilepsy and DS.