Scoliosis with Chiari I malformation without associated syringomyelia



Many patients with presumed idiopathic scoliosis are found to have Chiari I malformation (CM-I) on MRI. The objective of this study is to report on scoliosis progression in CM-I with no syringomyelia.


A retrospective review of patients with scoliosis and CM-I was conducted from 1997 to 2015. Patients with syringomyelia and/or non-idiopathic scoliosis were excluded. Clinical and radiographic characteristics were recorded at presentation and latest follow-up. CM-I was defined as the cerebellar tonsil extending 5 mm or more below the foramen magnum on MRI.


Thirty-two patients (72% female) with a mean age of 11 years (range 1–16) at scoliosis diagnosis were included. The average initial curve was 30.3° ± SD 16.3. The mean initial Chiari size was 9.6 mm SD ± 4.0. Fifteen (46.9%) experienced Chiari-related symptoms, and three (9%) patients underwent Posterior Fossa Decompression (PFD) to treat these symptoms. 10 (31%) patients went on to fusion, progressing on average 13.6° (95% CI 1.6–25.6°). No association was detected between decompression and either curve progression or fusion (p = 0.46, 0.60). For those who did not undergo fusion, curve magnitude progressed on average 1.0° (95% CI − 4.0 to 5.9°). There was no association between age, Chiari size, presence of symptoms, initial curve shape, or bracing treatment and fusion.


Patients with CM-I and scoliosis may not require surgical treatment, including PFD and fusion. Scoliosis curvature stabilized in the non-surgical population at an average progression of 1.0°. These results suggest that CM-I with no syringomyelia has minimal effect on scoliosis progression.

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NPO’N, PEM, MTH, JBE, LIK, DJH, BDS, ERS, MRP, MPG: Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work, Drafting the work or revising it critically for important intellectual content, Final approval for the version to be published.

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Correspondence to Michael P. Glotzbecker.

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Conflict of interest

Dr. Hresko reports other from Pediatric Orthopedics Society of NA, other from Medtronics, other from Nuvasive, other from Apifix, outside the submitted work. Dr. Emans reports other from Synthes/ DePuy/Johnson and Johnson, other from Zimmer/Biomet, outside the submitted work. Dr. Snyder reports other from AAOS, other from Orthopaedic Research Society, non-financial support from Orthopediatrics, other from Pediatric Orthopedic Society of North America, other from Scoliosis Research Society, outside the submitted work. Dr. Glotzbecker reports personal fees and other from nuvasive, other from medtronic, other from Depuy/synthes, other from Zimmer Biomet, other from orthobullets, other from PSSG, HSG, outside the submitted work. All other authors declare that they have no conflict of interest.

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O’Neill, N.P., Miller, P.E., Hresko, M.T. et al. Scoliosis with Chiari I malformation without associated syringomyelia. Spine Deform (2021).

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  • Idiopathic Scoliosis
  • Chiari I Malformation
  • Posterior Spinal Fusion
  • Posterior Fossa Decompression