Evaluation of medulla and cerebellar tonsilles in chiari type T malformation using magnetic resonance imaging histogram analysis

Chiari type I malformation (CMI) is characterized by variable degrees of herniation of the cerebellar tonsils from the foramen magnum caudally into the upper cervical spinal canal. Due to herniation, pressure changes occur at the level of foramen magnum. This study aimed to investigate microstructural changes in the medulla oblongata and cerebellar tonsils in CMI patients, which cannot be demonstrated by conventional Magnetic Resonance Imaging (MRI), by histogram analysis method. This study was planned retrospectively. Case and control groups who were imaged on a 1.5T MR (Philips Ingenia, Philips Healthcare, Best, the Netherlands) device between 2018 and 2022 were evaluated in the study. The study included 84 cases (45.7%) diagnosed with CMI and 100 healthy controls (54.3%). The medulla oblongata and cerebellar tonsils of both groups were retrospectively evaluated separately using T2-weighted (W) sagittal sequences. Sagittal T2-W MRI images were processed with a MATLAB© program specially written for this subject and texture analysis findings were obtained. Comparisons were made between the case and control groups by examining 32 parameters of the histogram in each image. In total, histogram parameters of 368 images obtained from the medulla oblongata and cerebellar tonsils of 184 cases (patients and control group) were evaluated. 63.1% of those in the patient group were women and 36.9% were men, and 63% of those in the control group were women and 37% were men. There was no significant difference between the groups in terms of gender (p=0.989). The average age of those in the patient group is 27.29±17.63 years, and the average age of those in the control group is 31.71±15.76 years. No significant difference was found between the groups in terms of age (p=0.074). A statistically significant difference was detected between CMI and the control group in 22 of 32 histogram parameters measured from the medulla oblongata (p<0.05). A statistically significant difference was detected between CMI and the control group in 22 of 32 histogram parameters measured from the cerebellar tonsil (p<0.05). According to the findings of the study, many histogram analysis parameters of the cerebellar tonsil and medulla oblongata, which were found to be normal on conventional MRI, were significantly different in CMI compared to the control group. These results suggest that possible microstructural changes in patients with CMI can be evaluated by histogram analysis. It may have beneficial effects on the diagnosis, treatment and prognosis of CMI. We think that further studies with larger scales and well-standardized measurement methods are necessary to provide more definitive evidence on this subject. Keywords: Chiari type I malformation, Magnetic Resonance Imaging, Histogram analysis, Medulla oblongata, Cerebellar tonsil