Predictors of progression of scoliosis after decompression of an Arnold Chiari I malformation

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 > 10degrees or to surgical range ( largest curve > 45degrees) 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 greater than or equal to 2 + and 50% of progressors had a thoracic kyphosis > 50degrees 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.