FIGURE 1.

Decision tree A and Kaplan–Meier survival functions B subsequent to recursive partitioning and selection of the tree that yielded the best 2 partitions. Of all the clinical variables included in the model, new postoperative neurological impairment most efficiently stratified patients by their overall survival risk. Group 1 (N = 161) denotes patients who did not have a new neurological impairment at 1-mo postoperative follow-up (median survival = 20.7 mo, 95% CI = 18.2-23.6), whereas those in group 2 (N = 67) had at least one impairment at follow-up (median survival = 13.2 mo, 95% CI = 12.1-15.7).