Spike rate did not decrease with contact-step distance from the SOZ in 22 ds003876 SEEG patients, but adjacent non-SOZ pairs had more spikes

We tested whether interictal spike rate decreases with distance from the clinical seizure-onset zone (SOZ) in an independent, multicenter SEEG cohort: 22 eligible patients from OpenNeuro ds003876, using archived features from 120-s interictal clips. The feature table lacked coordinates, so the preregistered primary test used contact-step distance along a shaft. The mean patient Spearman correlation was -0.095 (95% CI [-0.27, 0.09]; 13/22 negative; p = 0.32), and did not replicate a within-shaft gradient. Applying the same step-distance test to the HUP ds004100 positive-control features also gave a nonsignificant result (mean rho -0.119, p = 0.081); the cohort difference was p = 0.83. This does not refute the previously reported gradient using Euclidean distance in millimeters. In both cohorts, non-SOZ pairs one contact step from an SOZ pair had higher spike rates than pairs on shafts without SOZ (AUC 0.64 and 0.62, respectively). Spike rate remained high for distances of 1–4 steps and dropped at 5 or more steps and on other shafts. These results suggest a wider irritative zone without a graded fall over the first four contacts in these data. Interpretation is limited by absent coordinates, 120-s clips, automatic candidate-spike detection, shared contacts in adjacent bipolar pairs, small center-level sample sizes, and low post hoc power. The null primary result is not evidence of absence.

stereo-EEG · interictal spikes · epilepsy · seizure-onset zone · step distance · irritative zone