Abstracts

Rationale: The amygdala, hippocampus and medial prefrontal cortex (mPFC) are limbic brain regions implicated in emotional regulation. The aim of this study was to assess the connectivity of white matter tracts between these regions in patients with psychogenic non-epileptic seizures (PNES). Based on previous research, we hypothesized that white matter connectivity between the amygdalo-hippocampal complex (AHC) and mPFC in patients with PNES would differ from that of healthy control subjects (HCs). Methods: Eight patients with PNES and 8 age-and sex-matched HCs underwent high-resolution anatomical MRI and 32-direction diffusion tensor imaging (DTI) on a 3T MRI at the University of Alabama at Birmingham (n=9) and the University of Cincinnati (n=7). Image pre-processing and alignment were performed with Analysis of Functional NeuroImages (AFNI) software. Computation of DTI indices including fractional anisotropy (FA) and diffusion tensor tractography was performed using the Diffusion Toolkit and TrackVis software, respectively. Two regions of interest were defined to manually trace white matter fibers connecting the mPFC and AHC in each hemisphere for each subject (Fig.1). FA and the number of fibers for the left and right hemisphere tracts were compared between groups. Results: Patients with PNES exhibited a significantly greater number of white matter fibers in the right hemisphere tract compared to in the left hemisphere (P=0.035) with such difference not observed in HCs (P=0.81). There was a trend towards a greater number of white matter fibers between the mPFC and AHC of patients with PNES compared to HCs in the right hemisphere (p=0.091; Table 1) but not in the left hemisphere (p=0.55). Average FA of the fiber tracts was similar between patients with PNES and HCs in the right and left hemisphere (P=0.56 and P=0.78, respectively) and between hemispheres in both patients with PNES (P=0.55) and HCs (P=0.15). Conclusions: FA and number of fibers for the white matter tract connecting the mPFC and AHC were similar overall between patients with PNES and HCs. However, emotional processing observed in previous PNES studies may be related to the differences in the rightward asymmetry in the number of mPFC-AHC tract fibers in patients with PNES, along with the trend towards a greater number of fibers in their right hemispheric tract compared to HCs. This is the first study to investigate the structural connectivity in these regions involved in emotional regulation in patients with PNES.