Focal thalamocortical circuit abnormalities in sleep related epilepsy caused by focal cortical dysplasia type II.

Purpose To investigate the variations of the thalamocortical circuit between the focal cortical dysplasia (FCD) type II patients with sleep-related epilepsy (SRE) and those without SRE (non-SRE). Methods Patients with epilepsy who had histologically proven FCD type II were enrolled. Those without diffusion tensor image and 3-dimensional (3D) T1 MRI sequences were excluded. Thalamocortical structural connectivity to lesion and non-lesion regions was quantified using probabilistic tractography. Fractional anisotropy (FA) and mean diffusivity (MD) were computed. Results A total of 30 consecutive patients were included. Among them, 18 patients (60%) had SRE. Analysis of covariance showed that smaller lesion size was significantly associated with SRE (p=0.048). Compared to patients with non-SRE, patients with SRE showed a significant decrease in FA of thalamocortical projections to the lesion region (p=0.007). No difference was observed in the thalamocortical connectivity to the non-lesion region between patients with SRE and non-SRE. Among the patients with SRE, a significant decrease in FA of thalamocortical projections to the lesion region was noted compared with the contralateral homotopic non-lesion region (p=0.026). Conclusion The data provide evidence of disparity in thalamocortical projections to the lesion regions between SRE and non-SRE. This might indicate the underlying pathophysiology or neuroanatomical substrates of SRE related to the FCD type II.