Impact of Intraoperative Neuromonitoring Alert Resolution on Motor Deficits and Short-Term Outcomes After Spine Fusion.

INTRODUCTION

Intraoperative neurophysiologic monitoring (IONM) is commonly used during spinal surgery to track nerve function, with alerts indicating reduced nerve output and input. While IONM allows for surgical adjustments to mitigate nerve damage, its precise indications, effectiveness, and interpretation of alerts remain debated. Therefore, this study investigated the effect of IONM alert resolution on postoperative outcomes.

METHODS

All adult patients who underwent spinal fusion with IONM and experienced an alert in 2017 at a single tertiary center were included. Patients who experienced mortality or had incomplete physical examination documentation were excluded. Postoperative weakness/deficit was defined as a decrease of ≥1 point on a five-point motor strength scale at either immediate postoperative or 2-week follow-up compared with preoperative strength. Deficits were categorized as immediate only, persistent, or de novo (appearing at 2 weeks). IONM alert resolution was graded as full (return to baseline), partial (improvement but no return to baseline), or no resolution. Statistical analysis used Kruskal-Wallis tests (alpha = 0.05).

RESULTS

Our study included 115 patients, categorized by alert resolution: no resolution (n = 20), partial resolution (n = 22), and full resolution (n = 73). The partial and full resolution groups had higher cervical region involvement (86.4% and 67.1% vs. 25.0%, P < 0.001) compared with the no-resolution group. Otherwise, demographic characteristics were similar across groups. Notably, the degree of alert resolution was not associated with the rate, timing, or eventual resolution of postoperative motor deficits. Complications, length of stay, discharge disposition, and 90-day emergency department visits and readmissions were similar across groups.

CONCLUSION

Despite its frequent use in spine surgery, our findings suggest that the resolution of an IONM alert may not reliably predict the presence, timing, or reversibility of postoperative motor deficits. This suggests that neurologic injury, once indicated, may be more persistent than intraoperative monitoring alone can convey.