Is Intraoperative Neuromonitoring with SSEPs and EMG Predictable for Postoperative Neurologic Deficit in Posterior Lumbar Fusion Surgery? A Retrospective Cohort Analysis.

Abstract

Study DesignRetrospective, single-center cohort study.ObjectiveTo evaluate intraoperative neuromonitoring (IONM) with free-run electromyography (EMG) and somatosensory evoked potentials (SSEPs) during primary posterior lumbar interbody fusion (PLIF) for degenerative conditions and associations with postoperative motor deficits (PMD).MethodsPatients undergoing PLIF from 2015 to 2020 were reviewed. Revision fusions, deformity corrections, and procedures in proximity to the conus were excluded. Patient characteristics, comorbidities, surgical details and intraoperative EMG and SSEP recordings were reevaluated. PMDs were defined as any decline of ≥1/5 strength grade compared to preoperative. Test accuracy and predictive value of SSEP and EMG events for PMD were calculated.Results401 patients (48.9% females, mean age 61 years, mean BMI 28.6) were included. One- and two-level fusions accounted for 67.8% and 27.7% of cases, respectively, most commonly involving L4/5 (67.8%) and L5/S1 (51.4%). EMG events occurred in 29.4% (n = 118) and SSEP events in 4.5% (n = 18). SSEP events were significantly associated with PMD (P = 0.043), whereas EMG events were not (P = 0.463). In multivariable regression, SSEP events predicted PMD with odds ratios of 3.85 for any SSEP event and OR 10.41 for persistent SSEP signal loss (both P = 0.002). Test performance of SSEP was limited (sensitivity: 13.6%; positive predictive value 16.7%).ConclusionIn posterior lumbar interbody fusion, SSEP events are associated with postoperative motor deficits, whereas EMG events are not. However, the overall test accuracy of IONM in predicting neurologic deficits remains limited. Instead of routine utilization, IONM should be tailored to the individual case.