In 27 epilepsy patients, interictal discharges locked weakly to distant slow-wave phase, without reliable seizure-zone strengthening

In 27 epilepsy patients with 260 seconds of sleep SEEG per patient from OpenNeuro ds007118, ds007119, and ds007120 (version 1.0.0), interictal epileptiform discharges (IEDs) on bipolar depth pairs occurred at a preferred phase of the 0.5–2 Hz signal on distant normal reference pairs on other shafts. Mean excess mean resultant length (dMRL) over a circular-shift null was 0.026 (95% CI 0.016–0.037); 23 of 27 patients had positive values (sign-flip p = 1e-4, Holm p = 1e-4). The effect was small. Locking was not reliably stronger for seizure-onset-zone (SOZ) pairs: the within-patient SOZ minus non-SOZ dMRL difference was 0.016 (95% CI 0.001–0.031; median 0.0015), with 12 of 22 patients positive (p = 0.057; Holm p = 0.057). Secondary z-score analyses gave H1 z = 0.31 (p < 1e-4) and H2 z = 0.23 (p = 0.030, uncorrected); because z increased with IED count and SOZ pairs had more IEDs, this is not a clean test of locking strength. Distance analysis included only four patients and was not informative. Sleep stage was not scored and runs were assumed mostly NREM. IEDs detected on a reference pair within 0.5 s were removed, but volume conduction of the IED waveform was not excluded. The analysis plan was written and hashed before signal inspection.

intracranial EEG · SEEG · epilepsy · interictal epileptiform discharges · slow waves · phase locking · sleep · seizure onset zone