Abstracts

Rationale: Psychogenic nonepileptic seizures (PNES) are a common and debilitating problem. Patients with PNES may represent up to 10% of the population seen in outpatient epilepsy clinics, and 30% of patients referred for inpatient video-EEG monitoring at epilepsy centers. The present study sought to determine whether there could be specific neurophysiological changes associated with PNES in a group of patients who were prospectively investigated during prolonged video-EEG monitoring. Our main goal was to determine possible central nervous system regions presenting activation as a response to PNES produced by provocative tests. Methods: We assessed brain functional activation during seizures using single photon emission computerized tomography (SPECT) with 99m Tc-ECD in 30 patients with a diagnosis of PNES, whose seizures where induced by provocative tests, compared to ictal SPECT in 22 controls (patients with temporal lobe epilepsy) submitted to prolonged video-EEG monitoring. Then the ictal SPECT of patients with PNES were compared to the ictal SPECT of the subjects with temporal lobe epilepsy using statistical parametric mapping (SPM99). The images were transformed in DICOM format to ANALYZE format. Afterwards, they were converted to neurological convention and followed by covariance analysis, ultimately resulting in a set of t-values to identify significant changes between the two groups. Results: Comparing findings of regional cerebral blood flow (rCBF) in 22 subjects with partial complex temporal lobe seizures and 30 subjects with induced PNES, we found in the PNES group, a consistent increase of rCBF in the right precuneus (Brodman area 7, p=0,003) and in the right posterior cingulate gyrus (Brodman area 31, p=0,001), as well as a relative decrease of rCBF in the right amygdala (p=0,027). Details in the table. These results demonstrate a systematic neural correlate for PNES, involving the right precuneus and posterior cingulate gyrus, areas closely associated to the right temporoparietal junction. Conclusions: These preliminary findings provide new directions in an attempt to explain a psychobiological mechanism for PNES. Recent studies have implicated the right TPJ in several mental processes involving self-consciousness and self-agency¹. Therefore, our results suggest that the activation of associated areas could represent loss of self-agency and a lack of ""conscious intention"" observed in PNES. Moreover, the relative decrease of activity in the amygdala could be due to ictal activity in the temporal lobe epilepsy group, but could also be explained by the presence of abnormal interactions between the right amygdala and the right supplementary motor area, as recently observed in patients with conversion disorder². 1. Farrer C, Franck N, Georgieff N, Firth CD, Decety J, Jeannerod M. Modulating the experience of agency: a positron emission tomography study. Neuroimage 2003; 18:324-333. 2. Voon V, Brezing C, Gallea C, Ameli R, Roelofs K, LaFrance WC Jr, Hallett M. Emotional stimuli and motor conversion disorder. Brain 2010 May; 133 (Pt 5):1526-36.