Abstracts

Different thalamic nuclei may be targeted for neuromodulation in some pharmacoresistant epilepsies. The anterior (ANT), centromedian (CM), and pulvinar (PLV) nuclei are commonly targeted due to their anatomical connections to different regions but determining which nucleus is the best target for individual patients is unclear. This lack of certainty is partly due to limited knowledge of specific connectivity with epileptogenic zones.

We studied real-time interactions between these nuclei and seizure onset zones (SOZ⁺) in 10 drug-resistant epilepsy patients (ANT=4, PLV=4, CM=7) using sEEG. We analyzed interictal connectivity (weighted phase lag index) during seizure (D⁺) and seizure-free (D^-) days, comparing SOZ⁺ and non-seizure onset zones (SOZ^-) across various frequencies.

We observed varying connectivity patterns between the nuclei and different brain regions, confirming known anatomical connectivity, but more intriguingly, significant fluctuations within epileptogenic and non-epileptogenic regions, particularly noticeable during seizure days compared to seizure-free days.

ANT displayed stronger mesial temporal connectivity, with significant differences between SOZ⁺ and SOZ^- areas. On D^-, ANT had significantly stronger SOZ⁺ connections, mainly in θ, β, and γ bands, which decreased on D⁺ particularly in θ, suggesting that a strong ANT-SOZ⁺  connection could inhibit seizures in normal conditions (D^-), weakening during seizure days D⁺.

CM showed heightened SOZ⁺ connectivity in frontal, parietal and occipital regions. Remarkably for frontal areas, this was exclusive to D⁺ in a broadband range (δ-β₁), but absent during D^-, except in α. Perhaps on non-seizure days, weak SOZ⁺ connectivity does not enable seizures, while during D⁺, increased SOZ⁺ connectivity contributes to over-excitation.

PLV consistently had increased parietal and occipital SOZ⁺ connectivity. Intriguingly, in D⁺, the difference from SOZ^- became even more pronounced, primarily occurring in δ,θ,β₂ for parietal and δ-β₂ for occipital regions.

For lateral temporal areas, SOZ⁺ connectivity was lower than SOZ^- across all three nuclei. ANT maintained this distinction in both D⁺ and D^-, specifically in θ. PLV had weaker SOZ⁺ connectivity in θ,α,β₁ bands (θ only in D^-). CM displayed SOZ⁺<