Abstracts

Rationale: Psychogenic nonepileptic seizures (PNES) are thought to be a faulty response to stressful situations. In PNES, there is evidence for abnormal structural connectivity between emotion circuits and for altered functional connectivity between emotion and motor regulatory circuits. Patients with epilepsy also report stress as a major factor in seizure control. Patients with temporal lobe epilepsy may be particularly susceptible to the possibility of stress inducing seizures due to the involvement of medial temporal lobe structures in both, emotion regulation and seizure initiation. A comparison of the neural correlates of emotion processing in patients with PNES vs patients with epilepsy has not yet been conducted to date. In this study we investigate differences in fMRI facial emotion processing between patients with PNES and patients with left temporal lobe epilepsy (LTLE). Methods: 12 PNES subjects (2 male, ages 20-51, mean illness duration=4 years), 12 matched LTLE subjects (2 male, ages 20-56, mean illness duration=11 years), and 24 healthy controls (HCs) matched 2:1 to PNES patients (4 male, ages 20-55) underwent 3T fMRI while performing an emotional faces task. Subjects were presented a series of faces with different expressions (happy/sad/fearful/neutral) and instructed to identify male and female faces via button-press. After scanning, subjects were asked to indicate the expression on each previously presented face. Standard fMRI preprocessing, statistical modeling, and visualization were performed using AFNI software. Single-subject fMRI response to each emotion correctly identified in post-scan testing was modeled separately. Regression analyses covarying for BDI-II scores were performed to determine group differences in processing of each emotion (voxelwise p=0.005 uncorrected, cluster volume threshold=320 mm3). Results: PNES subjects exhibited worse depression symptom severity on the BDI-II than both LTLE subjects (p=0.034) and HCs (p=0.004), but LTLE subjects did not differ from HCs (p=0.18). Compared to patients with LTLE, patients with PNES exhibited increased activation for fearful faces in the left parahippocampal gyrus and left superior frontal gyrus, increased activation for happy faces in the right declive and increased activation for neutral faces in the left fusiform gyrus, right uncus and right declive (Fig. 1A). Both PNES and LTLE subjects exhibited overall decreased activation during emotion processing compared to HCs (Fig. 1B, C). Conclusions: While both patients with PNES and those with LTLE appear to have decreased responsiveness to emotional faces compared to their healthy counterparts, the altered emotional processing are sub-served by a different network of brain regions in each group. This study provides for the first time data in support of different mechanisms of stress-induced seizures in patients with PNES and epilepsy. Funding: UAB Epilepsy Center