Long term video/EEG prevents unnecessary vagus nerve stimulator implantation in patients with psychogenic nonepileptic seizures

Abstract

ObjectivePsychogenic nonepileptic seizures (PNES) are common paroxysmal events that mimic and can often be misdiagnosed as epileptic seizures. 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. MethodsWe evaluated patients who were implanted with a VNS by their primary neurologist for refractory seizures and who were referred to the Vanderbilt University epilepsy monitoring unit for a second opinion. The presumed diagnosis of epilepsy was based on abnormal routine EEG studies obtained by their primary neurologist. We evaluated these patients and recorded their typical spells between 2005 and 2009. We describe the results of 13 patients with VNS who were found to have PNES. The total number of patients with a VNS studied during this time was 60. ResultsNone of the patients had undergone prior long-term video/EEG monitoring to document the nature of their events. A total of 13 patients with an implanted VNS had exclusive PNES, 9 women and 4 men with a mean age of 38.2±10.4years. Mean age at seizure onset was 28.5±15.4years. Patients were taking two to four antiepileptic medications in addition to VNS at the time of video/EEG monitoring. The average latency from the time of VNS implantation to the confirmatory diagnosis was 2.8years. One to ten (median=3) of these patients’ typical seizures were recorded during video/EEG monitoring. All patients were subsequently discharged off antiepileptic medications, and five of these patients were discharged home with the VNS turned off. ConclusionA VNS may be implanted inappropriately in patients with PNES. As video/EEG monitoring may help in excluding the diagnosis of PNES and preventing unnecessary VNS implants, it should be a requirement before VNS implantation.