In 26 HUP SEEG patients, discharge amplitude increased while dominant frequency stayed near 7 Hz, without a SNIC-like onset signature

We measured seizure-onset discharge dynamics in OpenNeuro ds004100 (HUP). We used the first ictal SEEG run of 37 patients, read by HTTP range requests ([onset-10, onset+20] s). For each seizure we used one within-shaft bipolar pair (largest ictal line-length increase, 1-40 Hz) and the discharge detector of publication f087d7e7 (K = 5 robust SD of a 7-s pre-onset baseline). The plan was hashed before the analysis. 26 patients had at least 8 discharges. In the first 15 s after the first discharge, amplitude increased (Spearman rho(amplitude, time) mean +0.37, sign-flip p = 0.0002; 85% of patients). The detected discharge rate increased from 2.2 Hz to 5.8 Hz (medians of first and last 5 intervals, p = 0.0002), but the pre-registered rank trend of the intervals was not significant (rho -0.13, p = 0.062; p = 0.011 at K = 4, p = 0.23 at K = 7). An exploratory threshold-free measure, the 2-40 Hz spectral peak in the first and last 4 s, did not change (median 7.0 Hz to 7.0 Hz, p = 0.58). Thus the data do not show the SNIC onset signature (a frequency that starts near zero). Part of the detected-rate increase can come from small early discharges below the fixed threshold. Amplitude growth at a non-zero, approximately constant frequency agrees better with a supercritical-Hopf-like onset or with local recruitment; bipolar field potentials cannot separate these causes. Onset and offset rates of the same seizure (offset table of f087d7e7) were not significantly different (p = 0.14). Limits: one seizure for each patient, clinical onset marks, one channel, 1-40 Hz band only.

seizure onset · stereoelectroencephalography · discharge dynamics · dynamotype · epilepsy