Thalamic organization differentially contributes to clinical conditions in epilepsy

The thalamus plays an important role in key clinical conditions of focal temporal lobe epilepsy (TLE), but no investigation has examined whether the same thalamic local and connectome properties shape a patient's status across these different conditions.

This retrospective longitudinal MRI study used resting-state fMRI and structural imaging to identify whole-brain focal/regional and connectome-level features associated with six binary clinical conditions of TLE (pre/post-surgery, seizure and neurocognitive outcomes, pathology, seizure subtype, and SOZ lateralization) in 91 patients across two centers (age range: 15-65 years) and 85 matched healthy participants (age range: 18-60 years).

Across conditions, relative to all other brain regions, thalamic features exert the strongest influence. Specifically, thalamic focal and connectome intrinsic activity and gray matter volume are robustly associated with post-surgical reorganization. Pre-surgical thalamic hyperconnectivity predicts poorer seizure control, whereas post-surgical reorganization is not associated with either seizure outcome. Neuropsychological outcomes are subsequently examined and show associations with local ipsilateral thalamic properties. Namely, pre-surgical organization of the ipsilateral thalamus is associated with better preservation of cognitive performance, whereas post-surgical organization is associated with greater cognitive decline.

Our results expand and refine our understanding of the thalamus as a region showing robust and recurrent associations across multiple clinical conditions of TLE. Importantly, we distinguish its role in pre- versus post-surgical brain organization with respect to seizure and neuropsychological outcomes, highlighting its importance for planning and prognosis in epilepsy surgery.