In 22 SEEG patients, non-SOZ spike rates decreased with contact-step distance, but not after removing clinically spiking contacts

This pre-registered analysis tested whether interictal spike rate decreases with contact-step distance from the clinical seizure onset zone (SOZ) along stereoelectroencephalography (SEEG) shafts. Archived per-pair features from 43 patients and 728 bipolar pairs came from OpenNeuro ds007118, ds007119, and ds007120 (version 1.0.0). Among 22 patients with enough eligible non-SOZ pairs and defined correlations, the mean per-patient Spearman correlation between step distance and spike rate was -0.25 (median -0.22; bootstrap 95% CI [-0.42, -0.08]; one-sided sign-flip p=0.0054). The patient-centred profile decreased through the first three contact steps and was flat thereafter. Three secondary tests were not significant after Holm correction: adjustment for contact position (mean partial rho=-0.10, p=0.18, Holm p=0.53), restriction to pairs whose contacts were both labelled normal (mean rho=-0.09, p=0.24, Holm p=0.53), and comparison of distance-1 pairs with pairs on shafts without SOZ (AUC=0.54, p=0.30, Holm p=0.53). Thus the gradient was weak when clinically spiking contacts were removed, and collinearity prevents separating contact position from distance in these data. The SOZ versus non-SOZ spike-rate sanity check had AUC=0.68 (43 patients, p<0.0001). Five patients with at least four eligible pairs had no detected spikes and undefined correlations, so they were dropped. Measurements used a 30-120 s NREM window and a simple amplitude/envelope detector, not a validated clinical detector. Distance is measured in contacts, not millimetres. The results support a spike-rate gradient in this cohort but do not establish a clinical biomarker.

stereoelectroencephalography · interictal spikes · seizure onset zone · epilepsy · NREM sleep · contact-step distance · intracranial EEG