Introduction: Approximately half of patients with scoliosis in the setting of Chiari malformation type 1 (CM-I) ultimately require deformity correction despite posterior fossa decompression (PFD). Using a multi-institutional prospective registry of patients diagnosed with CM-I and syringomyelia, this study aimed to evaluate risk factors impacting the need for corrective scoliosis surgery post-PFD.
Methods: We conducted a retrospective review of patients prospectively enrolled in the Park-Reeves Syringomyelia Research Consortium registry. Patients with at least two years of follow-up data were included in our cohort. Descriptive statistics and multivariate regression were conducted using R. Statistical significance was set a priori at p<0.05.
Results: Forty-five (29.8%) patients required spinal fusion after PFD (mean time to fusion: 18.4 ± 14.9 months). Univariate analysis revealed that older age at scoliosis diagnosis (12.7 ± 3.1 months vs. 9.9 ± 3.9 months, p <0.001), age greater than or equal to 10 years at scoliosis diagnosis (84% vs. 50%, p <0.001), history of spinal dysraphism (11% vs. 2%, p = 0.014), greater preoperative scoliosis curve (46.9 ± 17.3° vs. 25.5 ± 12.0°, p <0.001), and preoperative scoliosis curve greater than or equal to 35° (76% vs. 19%, p <0.001) were associated with a need for spinal fusion. Clival canal angle was greater in the fusion group but not associated with a need for spinal fusion (147.8 ± 12.4° vs. 143.8 ± 11.3°, p = 0.068). Multivariate regression revealed that older age at scoliosis diagnosis and greater preoperative curve were independently associated with a need for spinal fusion.
Conclusions: Spinal fusion was necessary in only 30% of our patient cohort. Older age at scoliosis diagnosis and greater preoperative scoliosis curve were independent predictors of the need for spinal fusion within two years post-PFD. Long-term follow-up data is needed to assess the effectiveness of spinal fusion post-PFD.
Patient Care: Patients with Chiari malformation have a particularly high incidence of scoliosis, with estimates approaching 80% in some studies. Approximately half of these patients ultimately require spinal fusion for deformity correction despite neurosurgical intervention (posterior fossa decompression) for the Chiari malformation. Identification of factors predictive of the need for deformity correction in a large, multi-institutional cohort with long-term follow-up provides valuable information for patient and family counseling. Moreover, this research may identify modifiable risk factors that can be addressed to obviate the need for spinal fusion. Both of these outcomes would improve the quality of life for patients with Chiari-related scoliosis.
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Summarize the literature concerning the impact of posterior fossa decompression on the need for deformity correction in patients with Chiari malformation type 1 and scoliosis.
2. Discuss strengths and weaknesses of prior studies on the impact of posterior fossa decompression on the need for deformity correction in patients with Chiari malformation type 1 and scoliosis.
3. Identify factors predictive of the need for spinal fusion after posterior fossa decompression in patients with Chiari malformation type 1 and scoliosis.