In five patients, EZ pairs used more current to evoke visual percepts, but the effect was not significant after correction

We compared the reported current that evoked visual percepts for stereo-EEG (SEEG) pairs inside versus outside the clinically marked epileptogenic zone (EZ). The source contained 112 stimulation rows; 108 rows from 19 patients had usable electrode labels, including 15 EZ pairs. Only five patients had both EZ and non-EZ pairs. The mean within-patient EZ-minus-non-EZ difference was +0.68 log2 current (factor 1.6; 95% permutation-inversion CI +0.02 to +1.52; p = 0.046; Holm-adjusted p = 0.13). Three of five patients had a positive difference. The confidence interval was not inside the prespecified ±0.5 log2 equivalence margin, so the effect was not shown to be small. Secondary SOZ and pooled-slope estimates were also positive (+0.76 and +0.65 log2), but neither was significant after Holm correction (both adjusted p = 0.13). These data do not establish an EZ effect or a small effect. The source includes only stimulations that evoked a percept; the reported current is not a measured threshold, and there were no negative trials or fixed current staircase. The small sample and overlapping tests limit inference.

stereo-EEG · epileptogenic zone · visual percepts · cortical stimulation · current · visual prostheses · permutation test