Anatomical and functional alterations in patients with functional/dissociative seizures and posttraumatic stress...

Functional/dissociative seizures (FDS) involve alterations in emotional processing, agency, self-monitoring, and motor control. Post-traumatic stress disorder (PTSD) involves brain systems related to emotional processing, salience detection, memory, and cognitive control. FDS and PTSD converge on several clinical and neurobiological dimensions-including trauma-related vulnerability, emotional processing, dissociation, and alterations involving limbic and regulatory networks-while producing markedly different clinical manifestations. However, it remains unclear which neural abnormalities reflect these shared dimensions and which may be more specifically associated with the emergence of functional seizures.

The study included 25 FDS patients, 20 PTSD patients, and 23 healthy controls (HC) who underwent functional and structural 3T MRI. Functional connectivity between 12 predefined brain regions was analyzed using seed-to-voxel analysis. Cluster-based inference and Gaussian random field theory were applied with p-corrected <0.05 and p-uncorrected <0.001 thresholds. Cortical and subcortical structures, including specific hippocampal and amygdala subregions, were segmented using FreeSurfer, and volumes were expressed as mean ± SD.

FDS patients showed lower bilateral dentate gyrus volume (FDS: 142.75 ± 16.28, control: 157.75 ± 17.11, p-adj= 0.019) and greater left anterior cingulate cortical thickness (FDS: 2.85 ± 0.14, control: 2.75 ± 0.17, p-adj= 0.01). Compared with PTSD patients, FDS patients had lower right amygdala central nucleus (FDS: 39.81 ± 5.43, PTSD: 44.15 ± 4.15, p-adj= 0.01) and right pars orbitalis cortical thickness (FDS: 2.62 ± 0.19, PTSD: 2.75 ± 0.17, p-adj= 0.04). Hyperconnectivity was observed from the right hippocampus to the right temporoparietal junction (FDS vs. controls) and from the right insula to the orbitofrontal cortex (FDS vs. PTSD).

Anatomical and functional alterations were observed in FDS and PTSD groups versus HC and between FDS and PTSD groups. These findings suggest both shared and disorder-specific brain alterations in FDS and PTSD.