A method of evaluation of the shape of the human cerebellum: MRI study

Abstract

The variability of shape of an organ is one of the manifestations of its individual anatomical variability. Magnetic resonance imaging and other modern neurovisualization methods allow for in vivo determination of morphological characteristics of organs, considering their natural positioning. The aim of this study is to develop a method of evaluation of the shape of the human cerebellum based on the results of MR imaging morphometry. MR images of the brain were obtained from 30 subjects (15 male and 15 female aged between 20 and 40 years) without apparent brain pathology. MRI was performed using a 1.5 T MRI machine (Siemens Magnetom Symphony, Munich, Germany). The width of the cerebellum was determined in axial (Wax) and coronal (Wcor) planes, the length was determined in axial (Lax) and sagittal (Lsag) planes, the height was determined in coronal (Hcor) and sagittal (Hsag) planes. It was observed that the width of the cerebellum is determined almost equally in two different planes, the greater disparity is noted in the measurements of length and the maximum difference in values was found in the measurements of height. A moderate and statistically significant linear relationship was discovered between the variables Wax and Lax (r=0.48; p<0.01), as well as between Wcor and Hcor (r=0.39; p<0.05). Variability in the values of paired linear dimensions measured in a single plane and the absence of a functional relationship between them lead to variability in their ratios, or shape factors (Wax / Lax, Wcor / Hcor, Lsag / Hsag). These shape factors, in turn, influence the shape of intracerebellar structures, primarily the cerebellar nuclei. To evaluate the overall shape of the cerebellum, the following parameters have been proposed, which describe the relationships between one linear dimension of the cerebellum to the other two: relative width of the cerebellum (Wr=(Wax×Wcor) / (Lax×Hcor)), relative length of the cerebellum (Lr=(Lax×Lsag) / (Wax×Hsag)), and relative height of the cerebellum (Hr=(Hcor×Hsag) / (Wcor×Lsag)). Further analysis of these parameters defines which of the linear dimensions has a greater influence on the shape of the cerebellum, determining its structural features, such as the shape of its lobules, the course of its fissures, and the three-dimensional organization of its nuclei, among others. In vivo evaluation of cerebellar shape will facilitate improvements in the diagnosis of cerebellar disorders using MRI and will be valuable in conducting neuromorphological research studies.