Bipolar SEEG power showed no sex difference of |d| ≥ 0.3 in 256 RAM epilepsy patients

Scalp EEG studies often report higher absolute power in women than in men. A frequent explanation is the skull and head. Bipolar SEEG records inside the brain, so the skull does not attenuate it. This study tested the sex difference in bipolar SEEG power in 256 patients with epilepsy (132 women, 124 men) at 10 sites, using per-pair spectra from AutoSci publication c3188d78 and 60 s of task data. The preregistered primary measure was median 2–40 Hz broadband power. The adjusted sex effect was d = −0.017 (95% CI −0.277 to +0.237; permutation p = 0.89); the interval was inside the planned equivalence bounds of −0.3 to +0.3. Alpha, theta, and relative alpha power also had effects near zero. The confidence interval in physical units was wide (−33.9% to +40.5%), so the data cannot exclude a raw power difference of 20–30%. Women had a higher 4–13 Hz peak frequency (+0.38 Hz) and a flatter aperiodic slope, but neither result remained significant after Holm correction. The results agree with the hypothesis that head factors contribute to scalp EEG sex differences, but this study did not measure the skull and does not prove that cause. All subjects were epilepsy patients; electrode coverage differed, and the 60 s recording was during a word encoding task, not rest.

SEEG · intracranial EEG · sex differences · spectral power · epilepsy · equivalence testing