The management of pediatric Chiari I malformation with concomitant hydrocephalus: a multicenter retrospective analysis.

Background Chiari I malformation (CIM) rarely occurs alongside hydrocephalus (7-10%), and the relationship between the two-whether one is the cause or the effect of the other-remains contentious. Consequently, the optimal treatment approach for these patients is unclear. This multicenter, retrospective study analyzed management strategies and outcomes for children presenting with CIM and hydrocephalus, with or without syringomyelia.Methods We reviewed cases from 2005 to 2021 involving children (< 18 years) who underwent surgical treatment for CIM with hydrocephalus, with or without syringomyelia, at ten international pediatric neurosurgical centers. The primary outcome was the rate of revision surgery due to treatment failure, defined as the need for additional surgery due to unsatisfactory treatment of CIM and/or hydrocephalus by the initial intervention. Descriptive survival analyses and a step-down multivariable analysis to identify possible risk factors influencing the outcome were performed.Results The study included 49 patients (mean age 68.5 months, 65.3% male). Increased head circumference was noted in 40.8% of patients, and 24.4% reported preoperative headaches. Primary surgical treatments included CSF diversion in 61.2% of cases (42.9% VPS, 18.4% endoscopic third ventriculostomy [ETV]), intradural foramen magnum decompression (FMD) in 24.5%, and extradural FMD in 10.2%. The success-to-complication ratio was most favorable for extradural FMD (100% success, 20% complication), followed by ETV (44% success, 0% complication), VPS (76.2% success, 47.6% complication), and intradural FMD (33% success, 8.3% complication). At discharge and at the latest follow-up, 76% and 69% of patients showed improved Chicago Chiari Outcome Scale scores, respectively. The primary treatment modality and the bulging of the lamina terminalis were significant potential risk factors for the failure rate after multivariate analysis.Conclusion Our data reveals considerable heterogeneity in treatment approaches. Extradural FMD exhibited the most favorable success-to-complication ratio, while intradural FMD had the least favorable ratio. These findings provide some basis for informed discussion with families. Larger prospective studies are still needed to refine treatment strategies.