Estimation of Posterior Fossa Volume in Pediatric Patients with Chiari Malformations by the Cavalieri Principle

Chiari malformations (CMs) involve pathological hindbrain abnormalities reported to be correlated with a hypoplastic posterior fossa. This study calculates posterior fossa volume estimate using MRI. A retrospective review was conducted on patients who were admitted to our hospital. Clinical and radiological assessments were performed. Posterior fossa volumes (PFV) and intracranial volumes (ICV) were measured from head MRI scans using the Cavalieri principle. Forty CMs patients with a mean age of 9.5 years were identified. The mean PFV/ICV ratio for all the CMs patients (0.103) was found to be statistically smaller than that of the control patients (0.132, p < 0.05). It was concluded that the combination of MRI with the Cavalieri principle is a direct and accurate technique that can be applied safely for estimating the PFV and ICV. The PFV/ICV ratio is a predictor of CMs for the development of symptoms and the decision to perform surgery in children.