Abstracts

Rationale: Psychogenic nonepileptic seizures (PNES) are often misdiagnosed as epileptic seizures particularly if routine EEGs show interictal abnormalities. We conducted a retrospective case series of patients with PNES admitted for prolonged EEG-Video monitoring. The goal was to investigate the frequency of interictal EEG abnormalities during the admission. Methods: We reviewed the charts of 41 patients with PNES admitted for prolonged EEG-video monitoring at the University of Manitoba between April 2004 and May 2008. We included patients who had at least one clinical event atypical for an epileptic seizure (or other differential diagnoses of epilepsy) and not associated with any ictal epileptiform discharges. Results: 9 patients were thought to have both PNES and epileptic seizures. Of the 32 patients with only PNES, 8 (25%) had normal interictal EEGs during the admission, 8 (25%) had only non-specific slowing and 16 (50%) had spikes and/or sharp waves (these were not clearly epileptic in 10 (31%) patients). The most common locations of the epileptiform abnormality were bilateral temporal independently, followed by left temporal, right temporal, frontal, and multifocal, in descending order. Conclusions: We found a higher percentage of interictal epileptiform abnormalities compared to previous studies. This could be due to selection bias as most of our patients were admitted after an extensive outpatient workup including outpatient EEG-video recording that failed to establish a firm diagnosis. Our study emphasizes the importance of detailed analysis of ictal semiology and EEG-video monitoring in PNES.