Abstracts

Rationale: There is no literature or data on the efficacy of vagus nerve stimulation (VNS) in patients with brain tumor associated medically intractable epilepsy, a group which would benefit from this therapy. Methods: The epilepsy surgery databases at two separate epilepsy centers were reviewed to identify patients in whom a VNS was placed for tumor-related intractable epilepsy between January 1999 and February 2011. In addition, data from the VNS Therapy Patient Outcome Registry maintained by the manufacturer of the device, Cyberonics Inc. (Houston, TX), was queried to compare patients with and without a history and/or etiology of brain tumors. Pre-operative and post-operative seizure frequency and type as well as antiepileptic drug (AED) regimens and degree of tumor progression were evaluated. A case control analysis was implemented and patient outcome was measured by Engel classification, median seizure response, and responder rate (i.e. percentage of patients with at least 50% seizure reduction or equivalently Engel I, II, or III). Univariate and multivariate statistical analysis was performed using odds ratio and t tests to examine efficacy. Results: Sixteen patients from the two epilepsy centers were included in the study. Seven patients (43.8%) had an improved outcome (Engel I, II, or III) after an average follow-up of 39 months. The mean reduction in seizure frequency was 35.3% (p=0.005). After eliminating four patients who went on to have further surgery for tumor progression, mean seizure reduction was 48.4% (p=0.003). There was no significant change in AEDs. Seizure frequency decreased by 10.9% in patients in whom tumor progressed and 56.1% in patients with a stable tumor (p=0.034). The Outcome Registry analysis showed that in 196 brain tumor patients, VNS therapy reduced seizure frequency by 71% at 24 months with a 70% responder rate (> 50% seizure reduction). In a case control study comparing patients with and without tumors, there was no statistical difference in response rates. Conclusions: VNS therapy in individuals with brain tumor associated medically intractable epilepsy was shown to be equally effective at reducing seizure burden as in non-brain tumor patients through the first two years of treatment. Outcomes were notably better in patients with stable as opposed to progressing tumors. Therefore, these findings support the recommendation of VNS therapy in patients with brain tumor associated intractable epilepsy, especially in cases where imminent tumor progression is not expected.