Therapeutic Impact of Traction Release After C5 Nerve Root Motor Evoked Potential (MEP) Alerts in Cervical Spine Surgery.

ABSTRACT

STUDY DESIGN: A retrospective review of 40,919 cervical spine surgeries monitored with motor evoked potentials (MEPs) from a multi-institutional intraoperative neuromonitoring database. OBJECTIVE: The objective of this study was to determine the clinical impact of interventions prompted by C5 spinal nerve root MEP alerts. SUMMARY OF BACKGROUND DATA MEPs have been shown to diagnose acute C5 palsies, but additional data are needed regarding the clinical impact of interventions in response to C5 MEP alerts. MATERIALS AND METHODS: Procedures with isolated C5 MEP alerts were categorized as fully resolved, partially resolved, or unresolved based on the status of signals at closure. Clinical outcomes were based on neurological assessment in the immediate postoperative period. The sensitivity, specificity, likelihood ratios, and odds ratios (ORs) of C5 MEP alerts for acute C5 palsies were calculated. RESULTS: The odds of an acute C5 palsy greatly increased if there was a C5 MEP alert [OR=340.9; 95% confidence (CI) 173.0, 671.6; P<0.0001], and increased further if the alert persisted through closure (OR=820.8; 95% CI 398.1, 1692.0; P<0.0001). Relative to procedures with unresolved C5 MEP alerts, the risk of an acute C5 palsy significantly decreased if a C5 MEP alert was fully resolved by closure (OR=0.07; 95% CI 0.02, 0.25; P<0.0001). For alerts resolved during positioning or exposure, 90.9% were resolved with the release of positional traction, and for resolved alerts that occurred after exposure, 36.3% involved just traction release, 14.1% involved both traction release and surgical action, and 30.3% involved just surgical action. The sensitivity of C5 MEP alerts for acute C5 palsies was anesthetic dependent 89.7% (26/29) in the total intravenous regimen cohort but just 50.0% (10/20) in the inhalational anesthesia cohort. CONCLUSIONS: The timely release of positional traction is an effective intervention for resolving C5 MEP alerts and reducing the odds of an acute postoperative C5 palsy. Surgical maneuvers, such as the release of distraction or graft adjustment, should be attempted in conjunction with traction release depending on the surgical context of the alert. LEVEL OF EVIDENCE Level IV.