Assessment of Relationship between Clinical Manifestation of Chiari Malformation Type I and Volumetric Measurement of Cerebellar Tonsils Herniation within Foramen Magnum

Abstract

Introduction: Chiari malformation type I (CMI) is diagnosis based on clinical and radiological measurement of cerebellar tonsils herniation of 5mm or more below the foramen magnum (FM). The aim of the study was to determine the relationship between clinical presentation of CMI and cerebellar tonsils herniation measured in 3dimensions (3D), cerebellar tonsils volume and T/F volume ratio (cerebellar tonsils volume/foramen magnum). Methods: The study included 96 patients with CMI based on study sample size and power calculation.3D measurement of cerebellar tonsils was made, the volume of cerebellar tonsils was calculated using ellipsoid volume formula. The transverse diameter of FM measured and the volume of FM calculated using sphere formula. We computed non-parametric statistical tests and hypothesis testing to analyze correlation and variation of cerebellar tonsils measurements, cerebellar tonsils volume, and T/F volume ratio in relation to severity of myelopathy using mJOA (modified Japanese Orthopedics association) score and headache severity using NRS (Numerical Rate Score). Results: The finding showed a correlation between myelopathy severity and the volume of herniated cerebellar tonsils as well as correlation between myelopathy severity and T/F volume ratio (Cerebellar tonsil volume/Foramen magnum volume). There was also correlation between headache severity and cerebellar tonsil volume as well as T/F volume ratio. Conclusion: Consideration of both clinical presentation and radiological measurement in assessment of CMI is crucial, rather than considering only cut off of 5 mm descent of cerebellar tonsils herniation in midsaggital view. Cerebellar tonsils volume and T/F volume ratio are the indicators of severity of myelopathy and headache severity as shown in the study