Scoliosis associated with Chiari 1 malformations: the effect of suboccipital decompression on scoliosis curve progression: a preliminary study.

STUDY
DESIGN: A retrospective review of the effect of suboccipital decompression and duraplasty on curve progression in 22 patients who presented with scoliosis, syringomyelia, and a Chiari 1 malformation.
OBJECTIVES: To document the clinical characteristics of scoliosis in association with a Chiari 1 malformation, determine the effects of suboccipital decompression and duraplasty on scoliosis curve progression over time, and identify the clinical factors (age, gender, and curve characteristics) that may be associated with a clinical improvement in the scoliotic deformity after suboccipital decompression. SUMMARY OF BACKGROUND DATA: Prior publications have documented the clinical characteristics, signs, and symptoms of the Chiari 1 malformation. An association between Chiari 1 malformations, syringomyelia, and scoliosis has been recognized and reported. Several authors have also reported on the response of the scoliotic curve to Chiari 1 decompression, but the number of patients in these reports has been small. This cohort represents the largest number of patients to date (21) with Chiari 1 malformations, syringomyelia, and scoliosis who have been treated and followed over time in order to determine the effect of decompression on curve progression.
METHODS: A retrospective case review of 85 patients, age 16 years or less, who underwent posterior fossa decompression for a Chiari 1 malformation between 1990 and November 2000. A subset of 7 males and 15 females (22 of 85 total patients) who initially presented with scoliosis and were then found to have a Chiari 1 malformation was selected from this larger cohort for further review. The orthopedic and neurosurgical charts, spinal radiographs, and magnetic resonance imaging scans were then reviewed for each of these patients.
RESULTS: Twenty-one of the 22 patients who presented with scoliosis met the inclusion criteria of having a Chiari 1 malformation, scoliosis, and an unfused spine during the follow-up period after suboccipital decompression. One patient had a posterior spinal fusion before suboccipital decompression and was excluded from further review.
CONCLUSIONS: Thirteen patients of the 21 study patients (62%) had curve improvement or stabilization during the follow-up period. Eight of 21 patients (38%) had curve progression. Closer analysis reveals that the age, gender, and initial size of the scoliotic curve influenced the results of suboccipital decompression on the behavior of the scoliosis. Specifically, 10 of 11 patients (91%) who were less than 10 years of age at the time of suboccipital decompression have had their curves improve or stay the same during follow-up. In contrast, 5 of 7 female patients (72%) older than 10 years old with a curve greater than 40 degrees before suboccipital decompression have either been fused or are awaiting fusion.