Morphometric Analysis of the Posterior Fossa and Cervical Spinal Canal in Type 1 Chiari Malformation and Its Effects on Syringomyelia Development

Abstract

Introduction: Chiari malformation (CIM) is a congenital anomaly characterized by herniation of hindbrain structures through the foramen magnum into the cervical spinal canal (CSC). Although the pathogenesis of CIM has not been clearly defined, its relationship with the posterior fossa and CSC morphology is unclear. In this study, we aimed to perform morphometric analysis of both the posterior fossa and the CSC in CIM to investigate the correlation of measurements with each other and to reveal their effects on the development of syringomyelia (SM), which has not been previously reported. Methods: Magnetic resonance imaging images of 90 patients and 30 healthy individuals were retrospectively analyzed. Posterior fossa parameters and CSC diameters at all cervical vertebral levels were measured for each patient. The taper ratio of CSC was calculated separately for each group at the C1-C4 and C1-C7 levels. The average CSC shape was drawn for each group. Results: No statistically significant difference was detected between the age groups. A steeper taper ratio was detected when CIM was accompanied by SM. In addition, the posterior fossa had a narrower volume than the normal fossa in CIM. Conclusion: Morphometric analysis of both the posterior fossa and the CSC was performed using CIM for the first time in the literature. This is the first study to present the term “tapering” with an illustration.

Keywords

• chiari malformation
• posterior fossa
• syringomyelia
• morphometric analysis
• taper ratio