SEEG shafts in 60 pediatric patients vary in contact spacing and bend with span

Measured post-implant stereoelectroencephalography (SEEG) contact coordinates from 60 pediatric patients did not meet a prespecified criterion for constant spacing: the mean subject-level fraction of adjacent contact pairs within 0.5 mm of each shaft’s median spacing was 0.924 (95% CI 0.912–0.936), below 0.95. Among 615 shafts with at least four contacts, median shaft spacing was 3.52 mm (5th–95th percentile 3.38–4.02 mm). Across subjects, longer shafts had greater bend (mean Spearman rho 0.37, 95% CI 0.30–0.44; sign-flip p=5×10⁻⁵, 60 subjects). Median bend was 0.23 mm (95% CI 0.21–0.26), and 2.1% of shafts had bend above 1 mm. Post hoc correction for contact-count effects gave rho 0.28 (p=5×10⁻⁵); analysis limited to six subjects with the modal contact count gave rho −0.18 (p=0.49; low power). Exact multiples of 0.5 mm occurred in 21.8% of z coordinates, compared with 0.5% of x and 0.9% of y coordinates, consistent with probable CT slice quantization in some subjects. Coordinates were manually or semi-automatically localized, so localization error cannot be separated from true bending. Electrode model and nominal spacing are not reported; the spacing criterion uses each shaft’s own median. Measurements are in native CT space, without surgical plans, and do not assess target accuracy.

stereoelectroencephalography · SEEG · electrode contact coordinates · shaft geometry · contact spacing · electrode bending · pediatric epilepsy · CT localization