274 Predicting Reoperation in Surgically Managed Pediatric Chiari I Malformation

INTRODUCTION: Chiari I malformation (CMI) involves the herniation of cerebellar tonsils into the spinal canal, without brainstem involvement. When patients are symptomatic, surgical decompression is recommended, but reoperation rates can be as high as 30%. METHODS: Patients were queried from the 2007-2016 MarketScan Databases with the CPT code (61343) for CM decompression. To be included, a patient had to have been diagnosed with CMI, received decompressive surgery, and be eighteen or younger at the time of first operation. Patients were excluded if they had a diagnosis of any other class of Chiari malformation at any point. Next, the Elixhauser Comorbidity Index was constructed for each patient. These variables were then used as covariates in a multivariate regression model to predict reoperation following surgical decompression. Odds ratios, their corresponding confidence intervals, and metrics of significance were determined. RESULTS: 2,823 patients were included, with an average age of 10.4 (SD = 5.4). 169 (6.0%) patients underwent reoperations. As patient age at first operation increased, their reoperation rate decreased steadily (OR = 0.95, 95% CI = 0.93-0.98, p = 0.002). This association was primarily driven by a sharp decline in reoperation rate after the first three years of life. Patients in their first year had a mean reoperation rate of 17.6%; by age three, the reoperation rate declined to 5.2%, remaining fairly stable from age four (5.1%) to eighteen (4.9%). Use of duraplasty (OR = 0.75, 95% CI = 0.52-1.06, p = 0.112) did not alter the likelihood of reoperation. CONCLUSIONS: In a national pediatric cohort of patients with surgically managed Chiari I malformations, there was a significantly increased likelihood of reoperation in younger children. Our findings suggest that, when medically feasible, initial CMI surgery should be delayed until the age of three to minimize the chance of reoperation.