Abstracts

To identify predictive factors for the seizure-free outcome of vagus nerve stimulation (VNS) We included all patients who had undergone VNS implantation at our centre and had at least 1-year follow-up. All patients underwent a complete presurgical evaluation including a detailed clinical history, MRI, and long-term video-EEG with ictal and interictal recordings. After the implantation, the adjustment of stimulation parameters and concomitant antiepileptic drugs were at the discretion of the treating physician. The mean age of the patients was 22.7[plusmn]11.6 (range 7-53) years. Six of 47 patients (13%) became seizure-free after the VNS implantation. Only two variables showed a significant association with the seizure-free outcome: absence of bilateral interictal epileptiform discharges (IED) and presence of malformation of cortical development (MCD). The epilepsy duration showed a non-significant trend towards a negative association with the outcome. According to the logistic regression analysis, only absence of bilateral IED correlated independently with successful VNS therapy (p[lt]0.01). Bilateral IED (independent or bilateral synchronous) was found in one of six seizure-free patients and in 33 of 41 non-seizure-free patients. When bilateral IED were absent, the sensitivity for a seizure-free outcome was 0.83 (95% confidence interval: 0.44-0.97); and the specificity was 0.8 (95% confidence interval: 0.66-0.9). Bilateral IED was independently associated with the outcome of VNS. Our results are preliminary because they were based on a relatively small patient population. However, it may facilitate other prospective VNS studies enrolling larger numbers of patients to confirm our results (Supported by a grant from the [italic]Deutsche Forschungsgemeinschaft (DFG-Eb 111/2-2)[/italic])