Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion

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  • Division of Pediatric Neurosurgery, Department of Neurosurgery, Primary Children's Medical Center, University of Utah, Salt Lake City, Utah
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Object

Chiari malformation Type I (CM-I) is a congenital anomaly often treated by decompressive surgery. Patients who fail to respond to standard surgical management often have complex anomalies of the craniovertebral junction and brainstem compression, requiring reduction and occipitocervical fusion. The authors hypothesized that a subgroup of “complex” patients defined by specific radiographic risk factors may have a higher rate of requiring occipitocervical fusion.

Methods

A retrospective review was conducted of clinical and radiographic data in pediatric patients undergoing surgery for CM-I between 1995 and 2010. The following radiographic criteria were identified: scoliosis, syringomyelia, CM Type 1.5, medullary kinking, basilar invagination, tonsillar descent, craniocervical angulation (clivoaxial angle [CXA] < 125°), and ventral brainstem compression (pB–C2 ≥ 9 mm). A multivariate Cox regression analysis was used to determine the independent association between occipitocervical fusion and each variable.

Results

Of the 206 patients who underwent CM decompression with or without occipitocervical fusion during the study period, 101 had preoperative imaging available for review and formed the study population. Mean age at surgery was 9.1 years, and mean follow-up was 2.3 years. Eighty-two patients underwent suboccipital decompression alone (mean age 8.7 years). Nineteen patients underwent occipitocervical fusion (mean age 11.1 years), either as part of the initial surgical procedure or in a delayed fashion. Factors demonstrating a significantly increased risk of requiring fusion were basilar invagination (HR 9.8, 95% CI 2.2–44.2), CM 1.5 (HR 14.7, 95% CI 1.8–122.5), and CXA < 125° (HR 3.9, 95% CI 1.2–12.6).

Conclusions

Patients presenting with basilar invagination, CM 1.5, and CXA < 125° are at increased risk of requiring an occipitocervical fusion procedure either as an adjunct to initial surgical decompression or in a delayed fashion. Patients and their families should be counseled in regard to these findings as part of a preoperative CM evaluation.

Abbreviations used in this paper:CM = Chiari malformation; CM-I = CM Type I; CXA = clivoaxial angle; ICC = intraclass correlation coefficient.

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Contributor Notes

Address correspondence to: Douglas L. Brockmeyer, M.D., Division of Pediatric Neurosurgery, Primary Children's Medical Center, 100 North Mario Capecchi Drive, Suite 1475, Salt Lake City, Utah 84113. email: douglas.brockmeyer@hsc.utah.edu.

Please include this information when citing this paper: published online June 22, 2012; DOI: 10.3171/2012.3.PEDS11340.

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