Background
The aim of this study was to evaluate three-dimensional (3D) volumetric image reconstructions to identify morphological differences of the clivus and sphenoid sinus on computed tomography (CT) scans of Chiari malformation type I (CMI) patients and control subjects.
Methods
Axial CT studies on adult females for 30 CMI patients and 30 age and body mass index matched controls were used for this retrospective study. 3D volumetric reconstructions were created from the bone windows of axial data following image registration for position and orientation correction of the head. The volume, surface area, linear height, length, thickness and spatial displacement in the x, y and z axes were computed separately for the clivus and the sphenoid sinus for each subject; the area of the sella turcica at the mid-sagittal plane was also measured.
Results
Eleven parameters were found to be significantly different in CMI subjects as compared to controls. Most notably, clivus volume was reduced by 31% on average in CMI subjects. In contrast, we found that the sphenoid sinus volume was 38% larger on average in CMI subjects. Moreover, clivus length, height, width and thickness were 4.5, 2.8, 3 and 9.4 mm smaller, respectively, in CMI subjects as compared to controls. Our results also showed that the x-, y-, and z-centroid positions of the clivus and sphenoid sinus relative to the skull were not significantly different in CMI subjects as compared to controls. In addition, the sella turcica area at the mid-sagittal plane was 27% smaller in CMI subjects as compared to controls.
Discussion and Conclusions
This is the first study to demonstrate cephalometric differences in the 3D morphology of the clivus and sphenoid sinus between CMI subjects and controls. These findings can serve as additional diagnostic criteria for CMI and also further our understanding of the pathophysiology of CMI.