Thalamo-cortical synchrony shapes seizure expression in human temporal lobe epilepsy

In drug-resistant temporal lobe epilepsy (DR-TLE), some seizures are clinically symptomatic while others remain electrographic despite arising from the same seizure-onset zone (SOZ), suggesting that clinical expression reflects network dynamics beyond seizure origin. We examined whether thalamo-cortical network engagement differs between clinical (CS) and non-clinical seizures (NCS). We analyzed 286 seizures from 62 DR-TLE patients recorded using stereoelectroencephalography with pulvinar and/or anterior thalamic group coverage. Thalamo-cortical synchrony during the first 20 seconds of seizure onset was quantified as correlation between SEEG-derived time-frequency patterns in thalamic nuclei and the cortical SOZ. Synchrony was significantly stronger during CS than NCS (p < 0.0001, Cliff's δ > 0.6), including within-subject analyses, and was independent of other clinical variables, including postsurgical outcome. Linear mixed-effects modeling identified seizure type as the sole independent predictor of synchrony (p = 0.0069). These findings identify thalamo-cortical synchrony as a network-level feature associated with clinical seizure expression in DR-TLE.