Abstracts

Rationale: VNS has proven efficacious for the reduction of seizures in patients with epilepsy. The positive effect of VNS on interictal epileptiforme discharges (IEDs) on the EEG remains speculative. The purpose of this study was to show whether VNS induces changes in IEDs and to correlate these changes with long term seizure outcome. Methods: Patients treated with VNS were included in a prospective study. They underwent 24 hours EEG recording before the treatment, 6 months after VNS initiation and after 1 year of follow-up (FU). Automatic spike detection was performed using Reveal software (Persyst, Innovative EEG software TM). Prospective seizure frequency data was collected using seizure diaries. During the study AEDs remained unchanged. Clinical responders were defined as patients having > 50% seizure reduction. EEG responders were defined as patients having > 50% reduction in IEDs.Results: Eleven patients (5M, 6F) were included in the study and had a FU of 6 months, 8/11 (4M, 4F) had a FU of 1 year. At 6 months FU, 4/11 patients were clinical responders and 2/11 patients were EEG responders. None of the four clinical responders were EEG responders. At 1 year of FU, 2/8 patients were clinical responders and 6/8 patients were EEG responders. The 2 clinical responders were also EEG responders. Conclusions: The initial results from this study show no positive correlation between VNS induced changes in IEDs and seizure frequency at 6 months. At 12 months of FU, all clinical responders showed also EEG response. Further study in a larger patient population may corroborate these early results.