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BACKGROUND CONTEXT: Intraoperative monitoring (IOM) is consistently and convincingly reported to have high sensitivity and specificity for detecting neurological injury. However there is surprisingly little research or understanding in the literature to explain why some alert cases result in postoperative deficit but most do not. PURPOSE: Do interventions change the outcome following intraoperative monitoring alerts. STUDY DESIGN/SETTING: Retrospective review of 6700 cases. PATIENT SAMPLE: 110 patients with significant neuromonitoring changes intraoperatively. OUTCOME MEASURES: Neurological deficit at 1 month and 1 year. METHODS: A retrospective case review was carried out using 110 spinal surgery cases from a single institution. All had been classified as red alerts due to predefined significant IOM trace changes. They were divided into two groups depending on whether they had experienced postoperative deficit following the red alert (NNDþ) or not (NND-). A range of patient, operative, monitoring and intervention factors were collected and Chisquared and Fisher’s Exact test were used to find significant differences between the groups. RESULTS: 24 patients were NNDþ. Three factors were significant in determining which these were; patient age, blood loss and the monitoring modalities used. Interventions carried out did not differentiate NNDþ from NND-. CONCLUSIONS: There are few predictive factors in spinal surgery to define which patients will develop neurological deficit post-operative. Metalwork revision, steroids, imaging modalities used post-operatively, did not predict final neurological outcome. Patients less than 9 or with monitoring changes despite low blood loss had more chance of a real deficit post-operatively. Multi-modal monitoring was more accurate in predicting neurological deficit than SSEP alone. CONFLICTS OF INTEREST: None. FUNDING SOURCES: Research funding from Mesoblast Ltd.