Posterior Fossa Decompression Alone versus Craniovertebral Junction Fixation-Inclusive Strategies in Chiari I Malformation with Syringomyelia: A Propensity Score-Matched Retrospective Cohort Study.

Purpose: The optimal surgical strategy for patients with Chiari malformation type I (CMI) and syringomyelia remains debated, particularly regarding when additional craniovertebral junction (CVJ) stabilization is required in patients with anatomical abnormalities or suspected instability. Methods: We performed a propensity score-matched retrospective analysis of 145 pairs (N=290) based on ten preoperative variables, including detailed CVJ morphometrics. The primary outcome was the 6-month neurological dysfunction score. Secondary outcomes included syrinx regression, operative metrics, and severe complications (ICU stay >24 h, prolonged ventilation, reintubation, or tracheotomy). Results: Both groups improved significantly neurologically at 6 months (2.0 ± 1.2 vs 2.1 ± 1.3; mean difference 0.1, 95% CI -0.3 to 0.5; p=0.638), with parallel recovery trajectories (time-by-strategy interaction p=0.582). Syrinx width reduction did not differ significantly between groups (-3.6 vs -2.9 mm, p=0.245). CVJ fixation-inclusive strategies were associated with longer operative duration (p<0.001), greater blood loss (p<0.001), and a higher observed frequency of severe complications (13.1% vs 0%; p<0.001). Conclusion: In this propensity score-matched cohort, CVJ fixation-inclusive strategies were not associated with superior midterm neurological or radiographic outcomes compared with PFD alone after adjustment for measured baseline characteristics, while greater operative burden was observed in the fixation group. Residual confounding related to unmeasured dynamic instability cannot be excluded.