Abstracts

Vagal nerve stimulation (VNS) is believed to suppress seizures through alteration of polysynaptic vagal afferent function. Modulation of vagal activities occurs in the reticular activating system as well as central autonomic network and limbic system. Such stimulation consequently influences noradrenergic projections in a widespread fashion. Given the diffuse distribution of such vagal afferent network, we sought to determine if VNS use as adjunctive therapy for seizure control would have more overall impact in the care of patients with multifocal vs. unifocal epileptogenic findings on EEG. A retrospective medical chart review was undertaken of 27 patients with pharmacoresistant epilepsy who had VNS placement and serial follow-up for at least 18 months. In all cases, EEG confirmation of an epileptogenic focus was present. Thirteen patients had seizures emanating from a single, surgically unresectable, focus. Fourteen patients had EEG[apos]s demonstrating a multifocal epileptogenic EEG pattern. Baseline weekly seizure incidence was compared to post-VNS seizure frequency at 3,6,12, and 18 month intervals. Of the patients with unifocal epileptogenic EEG patterns, there was an average reduction in seizure occurrence of twenty-seven percent in the first eighteen months of follow-up. Patients with multifocal epileptogenic EEG findings had an overall reduction in seizures of forty-three percent during this time interval. By means of its diffuse effects on the noradrenergic system, in the initial eighteen months of use VNS therapy is more effective in reducing seizure incidence in persons with multifocal epilepsy than in patients with epilepsy due to a unifocal cortical epileptogenic site.