Figure 6.

Intraoperative monitoring predicts postoperative segmental motoneuron pool activation

(A) EMG recordings of PRM reflexes evoked in RF and TS at threshold, intraoperatively in the prone and postoperatively in the supine position; five superimposed responses each. RF- versus TS-selectivity of the stimulation intraoperatively was maintained postoperatively, with decreased thresholds.

(B) Transitions between categories from the prone to the supine position. Eighty-seven percent of the intraoperative datasets that were classified into either of the two RF-bias categories and 71% of those of the TS-bias category remained within the respective categories postoperatively. Data derived from 16 subjects.

(C) Thresholds of RF and TS responses evoked in the prone and supine positions. Data derived from 12 subjects. Thresholds for voltage- and current-controlled stimulators were pooled for the statistical testing, because pairwise comparisons were based on signed ranks (Wilcoxon test). Boxplots illustrate median thresholds as bold horizontal lines within boxes spanning the IQR and whiskers extending to the smallest and largest values that are not outliers (values 1.5–3 times the IQR; plotted as circles) or extreme values (values >3 times the IQR; asterisks). Brackets (dotted lines) indicate statistical significance, p < .05.