Abstracts

Rationale: Diffusion tensor imaging (DTI) has been applied to the investigation of white matter integrity in humans. However, unlike in epilepsy and other neurological disorders, DTI investigations in patients with psychogenic non-epileptic seizures (PNES) have been scarce. Thus, our objective was to investigate whole brain white matter integrity in patients with PNES. Methods: Included in this study were 14 patients diagnosed with PNES (13 females, mean age: 42.92 ± 14.61 years) and 14 age-matched healthy controls (HCs; 11 females, mean age: 41.71 ± 13.99). Diagnosis of PNES was confirmed by inpatient video-EEG monitoring; patients with additional types of seizures or who had an abnormal EEG indicating possible comorbid epilepsy were excluded. PNES were categorized as major motor (n=10), minor motor (n=1), waxy flexibility (n=2), and subjective (n=1) based on Griffith et al. (2007). All imaging was performed on a 3T MRI using 32-direction DTI sequence obtained as part of either routine evaluation (n=9) or a research study (n=19). Data preprocessing (alignment of DTI to anatomical scans, eddy current correction, image co-registration, computation of DTI indices) was carried out in AFNI followed by voxelwise analysis of multi-subject diffusion data using Tract-Based Spatial Statistics (TBSS) in FSL. Unpaired t-tests using α= 0.005 were carried out to compare DTI indices of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD) between PNES patients and HCs. Results: Numerous widespread areas of increased FA values were observed in patients with PNES including the bilateral corona radiata, temporal lobes, and cerebellar hemispheres, and the left basal ganglia. The cluster of higher FA values in the right corona radiata was much larger than that in left corona radiata. By contrast decreased FA values for PNES patients were observed only in the genu of corpus callosum, right lateral prefrontal and mesial frontal areas, and the pons. Conclusions: The most notable finding is that PNES patients show extensive areas of increased FA, but relatively few areas of decreased FA. In contrast to most pathologic processes, this pattern suggests increased, not decreased, connectivity. Increased FA values in patients with PNES were observed in the corona radiata where motor fibers are located, which may provide evidence of a stronger connection between emotional centers and motor cortex compared to HCs. Furthermore, lower FA in the genu of corpus callosum suggests a decrease in prefreontal hemispheric connections in PNES. Reference Griffith, N., et al. Relationship between semiology of psychogenic nonepileptic seizures and Minnesota Multiphasic Personality Inventory profile. Epilepsy & Behavior. 2007; 11(1):105-111.