Chiari I Malformations and Scoliosis: The Importance of Syringomyelia

Abstract

The association between Chiari I Malformation (CM-I) and scoliosis is well recognized, but it is unclear if surgical decompression of Chiari malformations alters scoliosis progression long-term in patients with associated syringomyelia (SM). The purpose of this study is to assess the effect of neurosurgical Chiari decompression on the natural history of scoliosis in CM-I patients with SM and CM-I patients without SM. Methods: Retrospectively, patients diagnosed with scoliosis (Cobb>10°), CM I, and SM over a 15-year period were identified. Patients with congenital, syndromic or concomitant causes of neuromuscular curves were excluded. Clinical and major curve characteristics were recorded at time of scoliosis diagnosis, before decompression and at last follow-up. Results: CM-I+ SM- Seventy-eight (25M, 53F) patients with a mean age of 9.3 years (1-19) at scoliosis diagnosis were included. Median follow-up was 5 years (range, 2-17). Forty-five patients were <10 years of age and 33 patients were ≥ 10 years of age at scoliosis diagnosis and neurosurgical decompression. Thirty of 78 (41%) patients presented with atypical curves as defined by criteria put forth by Spiegel et al. Sixty-seven (86%) patients underwent decompression, of which 26 (39%) improved, 18 (27%) stabilized and 23 (34%) progressed with 13 of the 23 (19%) requiring deformity correction surgery. The average scaled SM size decreased from 91.3±67.21 at presentation to 23.6±22.20 scaled units at follow-up (P<0.001). Multivariate analysis determined a one-unit reduction in syrinx scale increased the odds of curve improvement by 1% (OR=1.01; 95% CI = 1.00-1.02; p=0.01) and decreased the odds of fusion by 3% (OR=1.03; 95% CI=1.00-1.05; p=0.03). For each additional unit of syrinx scale at presentation, the odds of fusion increased by 3% (OR=1.03; 95% CI=1.00-1.05; p=0.03). CM-I: Only 51 (17M, 34F) patients with a mean age of 10 years (range, 1-18) at scoliosis diagnosis were included. Median follow-up was 3.6 years (IQR, 2.0 to 6.6). More than half of the cohort (29/51, 57%) was treated with bracing (Table 5). Curve magnitude progressed an average of 4.5 degrees (95% CI = 0.5 to 8.4 degrees) for the cohort from baseline to most-recent follow-up. Multivariable analysis determined that there was no association between change in curve magnitude and patient age, initial curve, Chiari size, or curve shape (all p>0.05). Conclusions: Improvement in SM scale size at follow-up is associated with spinal deformity improvement following CM-I decompression. Significance: SM improvement following decompression is associated with spinal deformity improvement at follow-up. Level of Evidence: 3.