O2134: The Dreaded Outcome: False Negative Intraoperative Neuromonitoring Alerts during Pediatric Spinal Deformity Surgery

Background: Intraoperative multimodal neuromonitoring (IONM) reduces the risk of postoperative spinal cord dysfunction in pediatric spinal deformity surgery by enabling corrective actions following alerts. However, a postoperative neurological deficit without an intraoperative alert, a false negative, is a rare but dreaded complication. Since little is known, this study aims to describe false negative (FN) IONM events and their immediate and final outcomes.

Methods: An institutional neuromonitoring database was reviewed (11/1992-4/2024) to identify consecutive patients (0–18 yrs) who underwent pediatric spine deformity surgery at one of our three tertiary care hospitals. Inclusion criteria were FN cases, defined as having a decline in neurologic function at conclusion of surgery without an IONM alert.

Results: Out of 5317 consecutive cases, 16 patients (0.32%) experienced post-surgical neurologic decline without an IONM alert. Mean age was 14 years (11-16). Diagnoses included idiopathic (n=5), kyphosis (n=3), spondylosis/spondylolisthesis (n=6), syndromic (n=1), and unknown (n=1). Surgeries included 14 posterior spinal fusions and 2 anterior/posterior fusions. Neuromonitoring modalities included somatosensory evoked potentials (SSEPs) (n=5), SSEPs and descending neurogenic-evoked potentials (DNEPs) (n=10), and SSEPs and transcranial motor-evoked potentials (TCeMEPs) (n=1). Five patients had preoperative neurologic abnormalities, including BLE weakness (n=3), weakness/paresthesia (n=1), and paresthesia alone (n=1). Among patients with preoperative neurologic abnormalities, 4 had sustained neurologic deficits at final exam (80%), compared to 9 patients among the 11 with normal preoperative neurologic exam (82%). Postoperatively, all patients experienced neurologic decline: 8 had weakness, 5 had both weakness and sensory deficits, 2 had monoplegia, and 1 had paraplegia. At final evaluation, 3 had complete recovery, 5 had partial recovery, 5 had no recovery and 3 had unknown outcomes. Among spinal cord level surgeries (n=9), outcomes included 1 complete recovery, 3 partial recoveries, 2 without recovery, and 3 with unknown outcomes. Among nerve root level surgeries for spondylolisthesis/spondyloptosis (n=7), outcomes included 2 complete recoveries, 2 partial recoveries, and 3 without recovery. In spinal cord and nerve root level surgeries with known outcomes, complete recovery occurred in 11% and 29% of patients with false negative IONM events, respectively. At the spinal cord level, 90% used SSEP/DNEP and 10% used SSEP/TcMEPs. Reoperations included decompression (n=3), instrumentation removal (n=2), and instrumentation revision (n=2).

Conclusion: This is the largest series of FN IONM cases in pediatric spinal deformity surgery, with 16 cases (0.32%) from 5317 surgeries. Only 3 (19%) patients fully recovered and 13 had persistent neurologic deficits at final exam (81% of FN cases, 0.2% of 5317 surgeries). With just one false negative using SSEP/TcMEP, these modalities are preferred over SSEP/DNEP to reduce false negatives in spinal cord surgeries.