Multi-Dimensional Morphometric and Volumetric Analysis of the Posterior Cranial Fossa to Study Type I Chiari Malformation

Abstract

Chiari malformation type I (CM-1) is a complex disorder in which tonsillar herniation through the foramen magnum manifests with a spectrum of clinical symptoms. This work analyzes morphometric and volumetric characteristics of CM-1 patients. With Institutional Review Board (IRB) approval, we retrospectively reviewed a total of 72 adult CM-1 patients and 26 healthy adult volunteers who underwent volumetric magnetic resonance brain imaging. Clinical data was retrospectively extracted from the electronic medical record. We analyzed multi-dimensional morphometric and volumetric features within the posterior cranial fossa and correlated these features with syrinx formation and the decision to undergo surgical decompression. In our study, CM-1 patients had decreased cerebellar, brainstem and 4th ventricular volumes but larger tonsillar volume with increased total tonsillar length. CM-1 patients who underwent surgery had significantly more neural tissue within the cross-sectional area of cisterna magna. Logistic regression demonstrated that combining neural tissue at foramen magnum with cerebellar & 4th ventricular volumes led to great degree of correlation with syrinx formation (AUC 0.911). Our findings suggest that the amount of tissue at the foramen magnum correlates with CM-1 patients who underwent decompressive surgery, more so than tonsillar length. Additionally, the combination of neural tissue at foramen magnum, cerebellar & 4th ventricular volumes led to great degree of correlation with syrinx formation. Together, these findings suggest that a global compressive phenomenon within the posterior fossa leads to CM-1 symptomatology and syrinx formation.