Motor evoked potential recovery with surgeon interventions and neurologic outcomes: A meta-analysis and structural causal model for spine deformity surgeries.

OBJECTIVE

To improve estimates of motor evoked potential (MEP) performance during spine deformity surgeries by accounting for potential confounders.

METHODS

A meta-analysis of MEPs for spine deformity surgeries determined the probability of a MEP deterioration which recovered by the end of surgery, P(RSC), and the conditional probability of no new post-operative deficit given an RSC, P(NND|RSC), stratified by category of intraoperative adverse event associated with the MEP deterioration. A structural causal model (SCM) and propensity score matching accounted for intraoperative adverse events and patient diagnosis as potential confounders.

RESULTS

MEPs changes (either reversible, RSC or irreversible, IRREV) were reported for 295 of 5055 cases (6%) in 21 studies. The probability of no new motor deficit, P(NND), plotted against the probability of a RSC, P(RSC), for studies in the meta-analysis was highly significant (r = 0.71, p < 0.001). P(RSC) was 0.76 for an alert associated with correction, less for osteotomies (0.48, p = 0.0008), and tended to be higher for hypotension (0.92, p = 0.06). P(NND|RSC) was 0.94 for correction, less for positioning (0.82), and osteotomies (0.86), and greater for hypotension (1.0). In the SCM, a RSC after an alert was a highly significant and independent predictor of no new motor deficits (odds 25.2, p < 0.001).

CONCLUSION

There are significant differences in P(RSC) for hypotension and osteotomies, and in P(NND) for osteotomies and instrumentation, compared to correction. P(RSC) is a significant and independent predictor of outcomes.

SIGNIFICANCE: When MEPs are used for spine deformity surgeries, accounting for adverse events associated with an alert and patient diagnosis as potential confounders is expected to improve RSC prediction of post-operative outcomes and estimates of RSC efficacy in improving outcomes.