Study Design. Retrospective study of patients with scoliosis and an Arnold Chiari I malformation requiring operative management.

Objectives. Determine the factors that could predict whether a particular spinal deformity might progress despite neurosurgical management of Arnold Chiari I malformation.

Summary of Background Data. Few studies have documented the relationship between diagnosis and treatment of Arnold Chiari I malformation and associated spinal deformities. Most studies mix neural axis abnormalities and contain limited information about the spinal deformity.

Methods. Medical records, radiographs, and magnetic resonance images of patients were evaluated focusing on age and findings at presentation, characteristics of presenting and follow-up spinal deformities, and the specifics of neurosurgical and orthopedic management. Patients were divided into two groups: those whose curves progressed >10° or to surgical range (largest curve >45°) after neurosurgical intervention (progressors) and those whose curves stabilized or decreased (nonprogressors).

Results. Eight progressors presented at an average age of 11.4 years (range 2–19) and were followed for 6.3 years (range 2–15). Seven nonprogressors presented at 6.5 years of age (range 5–10) and were followed for 6.6 years (range 3.5–14). Neurosurgical procedures were equivalent in both groups; however, surgical revisions were required in 3 out of 8 progressors and 1 out of 7 nonprogressors. All progressors had a double scoliosis curve; but only one nonprogressor had a double curve. Six out of 8 progressors and 0 out of 7 nonprogressors had a rotation ≥2+ and 50% of progressors had a thoracic kyphosis >50° compared to 1 out of 7 nonprogressors.

Conclusions. In this series, progression of spinal deformity after neurosurgical management of Arnold Chiari I malformation was associated with later age at neurosurgical decompressions and initial neurologic symptoms, double scoliosis curve patterns, kyphosis, rotation, and larger curve at presentation.

With the advent of magnetic resonance imaging (MRI), spine surgeons have developed an increased awareness of neurologic abnormalities associated with spinal deformity. Several studies have defined curve patterns and clinical presentations that warrant MRI evaluation. 1–6 As a result, Arnold Chiari Type I malformations (ACM-I) and syringomyelia have been discovered with increasing frequency in patients with a spinal deformity. In some cases, the spinal deformity is the first sign of an underlying neurologic abnormality. Some case reports and anecdotal evidence support that some curves improve (or resolve completely) after neurosurgical management of an ACM-I. 7–9 In other reports, the spinal deformity progresses relentlessly. 10–13

In the past decade, a few studies 1,8,9,11–16 have explored the relationship between the diagnosis and treatment of ACM-I and the associated spinal deformity. All series are small, and their conclusions often contradict previous reports. Most studies do not elaborate on the specifics of the spinal deformity at presentation. The current authors studied children who required operative neurosurgical management of an ACM-I at a major regional center for pediatric orthopedic and neurosurgery to investigate factors that might predict curve progression.