Predictors of syrinx presentation and outcomes in pediatric Chiari malformation type I: a single institution experience of 218 consecutive syrinx patients

Purpose Chiari I malformation (CM-I) in pediatric patients can impose substantial neurologic and functional impairment. Additionally, the presence of syrinx is often a harbinger of clinical compromise, but little attention has been devoted to identifying features associated with syrinx development and the clinical impact of syrinx resolution. Therefore, this study aims to identify clinical and radiographic variables associated with preoperative syrinx presence and postoperative syrinx reduction in pediatric patients with CM-I and determine the relationship between postoperative syrinx reduction and clinical symptom improvement. Methods The authors performed a retrospective analysis of 435 consecutive pediatric patients who underwent surgical treatment of CM-I from 2001 to 2021 at a single tertiary pediatric medical center. All patients underwent pre- and postoperative MRI, and clinical and radiographic variables were recorded and subject to inferential analysis. Results Syrinx at presentation was independently associated with symptoms of spinal cord dysfunction at presentation (OR 2.17 (95% CI 1.05–4.48); p = 0.036), scoliosis (OR 5.33 (2.34–10.86); p = 0.001), and greater pB-C2 (posterior basion to C2 distance) measurement length (OR 1.14 (95% CI 1.01–1.30); p = 0.040). Syrinx at presentation was inversely associated with tussive headaches at presentation (OR 0.27 (95% CI 0.16–0.47); p = 0.001) and cranial nerve deficits at presentation (OR 0.49 (95% CI 0.26–0.92); p = 0.025). Postoperatively, patients with radiographic evidence of syrinx improvement had greater rates of symptom improvement (93.1% vs 82.1%; p = 0.049), better CCOS scores (15.4 vs 14.2; p = 0.001), and decreased rates of readmission (6.0% vs 25.0%, p = 0.002) and reoperation (0.5% vs 35.7%; p = 0.001). The difference in syrinx resolution was similar but not statistically significant (10.3% vs 16.7%; p = 0.251). AO joint anomaly (OR 0.20, 95% CI 0.04–0.95; p = 0.026) and foramen magnum diameter (OR 1.12, 95% CI 1.00–1.25; p = 0.049) were the only independent predictors of syrinx improvement, and surgical technique was the only predictor for syrinx resolution (OR 2.44, 95% CI 1.08–5.50; p = 0.031). Patients that underwent tonsil reduction surgery whose syrinx improved had a wider foramen magnum diameter than those whose did not improve (34.3 vs 31.7; p = 0.028). Conclusions Radiographic syrinx improvement is associated with greater rates of symptom improvement and less readmiss