Intraoperative Neuromonitoring as an Added Safety Measure to Prevent Iatrogenic Injury in Chiari I Malformation Surgery

PURPOSE To assess the surgical utility of intraoperative neuromonitoring (IONM) as a safety measure to ensure safe operative conditions in Chiari I malformation patients undergoing FMD. METHODS This represents a retrospective cohort study examining symptomatic Chiari I malformation patients at one tertiary care center that underwent FMD using IONM between January 2017 and 2022. Brainstem auditory evoked response (BAER), somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), and electromyography (EMG) were utilized in all cases. Patients with and without IONM changes were directly compared. Linear regression analysis was completed to identify variables predictive of IONM changes. RESULTS Forty-eight patients met inclusion criteria, with ages ranging from 1 to 52 years (mean 15 years). The incidence of co-existing syringomyelia was 40% (n = 19), scoliosis 15% (n = 7), and tethered cord 0%. Four patients (8%) experienced IONM changes intraoperatively, all manifesting as decreases in MEPs. These were corrected by increasing mean arterial pressure (n = 1) or patient and head and neck repositioning (n = 3). Scoliosis predicted IONM changes (Beta 0.30, p = 0.04). Absence of syringomyelia trended towards predicting against IONM changes, however this did not reach significance (Beta − 0.24, p = 0.09). CONCLUSION IONM may be a useful tool to help facilitate safe FMD in Chiari I malformation patients. While this represents a single center experience with a small patient sample size, our data suggests that the utilization of IONM as a safety measure to prevent iatrogenic temporary or permanent neurologic deficit may be beneficial and warrants further study.