Scoliosis Associated with Chiari Malformation–Surgical Decision-Making

To review the current evidence regarding scoliosis associated with Chiari malformation type I (CM-I) and syringomyelia, emphasizing pathophysiology, radiological characteristics, natural history, and surgical decision-making. A narrative review of the literature was performed using the PubMed/MEDLINE, Scopus, and Google Scholar databases. Studies published between 1990 and 2026 addressing CM-associated scoliosis, syringomyelia, posterior fossa decompression, and spinal deformity correction were reviewed. Priority was given to landmark clinical series, cohort studies, and systematic reviews with relevance to surgical management. Scoliosis is present in approximately 25 to 85% of patients with CM-I, particularly in the presence of syringomyelia. Several radiological and clinical findings may suggest nonidiopathic scoliosis, including left thoracic curves, early onset deformity, rapid progression, hyperreflexia, and atypical neurological findings. Current evidence suggests that syringomyelia plays a central role in scoliosis pathogenesis, through asymmetric spinal cord dysfunction and paraspinal muscle imbalance. Posterior fossa decompression may stabilize or partially improve scoliosis, particularly in younger patients with small curves (< 30–35°). However, larger curves and patients approaching skeletal maturity frequently require definitive spinal deformity surgery despite successful craniocervical decompression. Important predictors of progression include larger Cobb angles, extensive syrinx morphology, thoracic syrinx extension, and advanced skeletal maturity. Scoliosis associated with CM-I represents a distinct entity from idiopathic scoliosis, requiring individualized multidisciplinary management. Posterior fossa decompression is generally recommended before deformity correction in patients with significant syringomyelia, although severe structural curves frequently require definitive scoliosis surgery. Early recognition of neuroaxial abnormalities is essential to optimize outcomes and reduce neurological complications.