Abstracts

Rationale: Psychogenic Nonepileptic Spells (PNES) are common spells that mimic epilepsy and can often be misdiagnosed as epilepsy. PNES account for 10 to 40 % of patients referred to epilepsy centers. Patients with uncontrolled PNES are at times subjected to vagus nerve stimulator (VNS) implantation. We report a series of such referred patients studied with video EEG monitoring at our institution Methods: We evaluated patients who were implanted with VNS by their primary neurologists for refractory spells and who were referred to the Vanderbilt University inpatient video-EEG monitoring for second opinion. The presumed diagnosis of epilepsy was based on abnormal routine EEG studies obtained by their primary neurologists. We evaluated these patients and recorded their typical spells between years 2005-2009. We present the results of 12 patients with VNS who were found to have psychogenic nonepileptic spells. Results: None of these patients had prior long term video-EEG monitoring to document the nature of their spells. A total of 12 patients with implanted VNS had exclusive PNES, nine females and three males with a mean age 38.7 ± 10.7 years . Mean age of onset of spells was 30.1 ± 14.9 years. Patients were on 2-4 antiepileptic medications in addition to VNS at the time of video EEG monitoring. From the time of VNS implant, an average latency time of 2.7 years before the confirmatory diagnosis was made in our video-EEG. Patients had 1-10 (median 3) of their typical spells recorded during video EEG monitoring. All patients were subsequently discharged off antiepileptic medications while five of these patients were discharged home with VNS turned off. Conclusions: VNS should only be used in patients who have an unequivocal diagnosis of epilepsy. A definitive diagnosis of epilepsy can be made by recording typical spells with video-EEG. Video-EEG may help in excluding the diagnosis of PNES and thus preventing the unnecessary surgical procedure of VNS implants.