Do the waveform transition patterns after intraoperative neurophysiological monitoring alerts indicate the postoperative neurological outcomes after spinal correction surgery?

Abstract

Intraoperative neurophysiological monitoring (IONM) alerts during spinal deformity surgery require timely intervention, but the prognostic significance of different waveform transition patterns following these alerts remains inadequately characterized. This study aimed to classify IONM waveform transition patterns after critical alerts and evaluate their association with immediate and long-term postoperative neurological outcomes. A single-center retrospective cohort study. Thirty-seven out of 1994 patients (1.9%) who experienced significant IONM alerts during spinal deformity correction surgery between July 2015 and June 2022. Physiologic Measures: IONM waveform recovery (full, partial, or none). Functional Measures: Neurological status (no deficit, partial deficit, or complete paralysis) assessed immediately postoperation and during 24-month follow-up. Patients were categorized into five distinct IONM patterns based on waveform recovery dynamics and postoperative neurological status. Demographic, surgical, and radiographic factors were compared across groups. Due to the small sample size, analyses were primarily descriptive. Between-group comparisons were performed using Fisher's exact test for categorical variables.. Five waveform patterns were identified: Pattern A (full recovery, no deficits; 21.6%), B1 (partial recovery, no deficits; 13.5%), B2 (partial recovery, partial deficits; 24.3%), C1 (no recovery, partial deficits; 32.4%), and C2 (no recovery, complete paralysis; 8.1%). Exploratory analyses suggested that global kyphosis >90°, alerts during osteotomy, three-column osteotomy, blood loss >3000 mL, and preoperative spinal cord abnormalities were more frequent in patients with irreversible alerts and deficits. At 2-year follow-up, 91.7% of patients with initial neurological deficits showed improvement, suggesting that IONM waveform recovery may be associated with favorable neurological prognosis. IONM waveform transition patterns following critical alerts demonstrate an significant association with postoperative neurological outcomes. Recovery trajectories varied across patterns: all Pattern B2 patients recovered within 6 months, while Pattern C patients showed gradual improvement over 24 months, with 91.7% of affected patients achieving favorable outcomes by 24-month follow-up, underscoring the importance of timely intervention during spinal deformity surgery.