Posterior fossa decompression in syndromic children with chiari-like posterior fossa crowding: a nationwide US-based study

INTRODUCTION: Posterior fossa crowding, due to cerebellar tonsil herniation, often requires surgery with posterior fossa decompression (PFD). Although most cases are due to a Chiari-1 malformation (CM1), some are due to concomitant congenital conditions, mimicking a radiological CM1. The aim of this study was to compare PFD outcomes between CM1 and the syndromic Chiari-like crowding of the posterior fossa. A national pediatric surgical database was used to compare baseline characteristics and short-term postoperative outcomes. METHODS: Pediatric patients undergoing PFD (2012-2021) were identified in the ACS NSQIP-P database. Baseline characteristics and 30-day outcomes were compared between syndromic and non-syndromic cases. Multivariate logistic regression identified factors associated with readmission and reoperation. RESULTS: Among 6,910 patients who underwent PFD, 752 (11%) had associated syndromes or conditions. The most common syndromes were chondrodystrophies (28%), fetal alcohol syndrome (14%), and Klippel-Feil syndrome (10%). Syndromic patients were younger, had lower BMI, and exhibited a significantly higher prevalence of comorbidities, including pulmonary, gastrointestinal, cardiac, and neurological conditions (all p < 0.001). They also experienced longer hospital stays (mean 5.17 vs. 3.64 days; p = 0.010), higher rates of 30-day complications (12% vs. 8.7%; p = 0.003), readmissions (9.4% vs. 7.1%; p = 0.021), and reoperations (6.6% vs. 2.9%; p < 0.001). In adjusted analysis, syndromic cases were not independently associated with increased 30-day complications or readmissions but remained significantly associated with 30-day reoperation (OR 1.51; 95% CI 1.03-2.19; p = 0.032). CONCLUSION: The syndromic Chiari-like condition is associated with distinct baseline characteristics and higher short-term complication rates following PFD compared to true CM1. While syndromic status was independently associated with reoperation, it was not an independent predictor of overall complications or readmissions. These findings suggest that patients with syndromes mimicking CM1 represent a clinically and etiologically distinct entity, warranting tailored management and further investigation.