Abstracts

Rationale: To report the seizure frequency outcomes and clinical characteristics of epilepsy patients who received a second modality of neurostimulation after the first modality failed to yield satisfactory results.

Methods: We reviewed the medical charts of adult patients with medication-resistant epilepsy who presented to our center after an initial treatment with a vagus nerve stimulator (VNS), which did not achieve desirable results. These patients were subsequently treated with another neurostimulation modality, using either deep brain stimulation (DBS) or a responsive neurostimulation system (RNS). All patients underwent a comprehensive surgical evaluation and were discussed in our multidisciplinary surgical epilepsy conference during the period from 2010 to 2022. We report the percentage reduction of seizures at the last follow-up after the second modality was implemented.


Results: Twenty patients (10 female) were included, with a mean (±SD) age of 42 (±15) years. None of the patients had undergone resective epilepsy surgery prior to the neurostimulation devices, and thirteen patients underwent intracranial EEG monitoring as part of their evaluations. Fourteen patients had RNS as the second modality, while six underwent DBS. Three patients had a family history of epilepsy, with one having a GABRA1 mutation. One patient had genetically confirmed Rett syndrome, three had malformations of cortical development, two had developmental delay, one had childhood viral encephalitis, and one was diagnosed with Rasmussen encephalitis. Five patients reported their first seizures at age 18 or older. Four patients had generalized epilepsy, and four had multifocal epilepsy. The mean number of anti-seizure medications at the time of the second surgical evaluation was 3 (±1). There was an average of 8 (±5) years between the VNS and the second modality. Patients were followed up for a median of 4.5 years (IQR: 4.7 years). At the most recent follow-up, 11 patients reported at least a 50% reduction in seizures (with 2 achieving seizure freedom), and 6 had no change in seizure frequency compared to their average baseline before the second neurostimulation was implemented. Among the patients who achieved seizure freedom, the first patient had no lesions on imaging and underwent DBS. The second patient underwent RNS for bilateral mesial temporal sclerosis, which controlled the seizures on the right side but required subsequent resective surgery to control the left-sided seizures.


Conclusions: Although rare, achieving seizure freedom is possible with a second neurostimulation modality in patients for whom the first modality did not yield desirable results. Even when seizure freedom is not achieved, the rate of significant benefit seems encouraging in such a challenging group of patients.

Funding: None.