High-Resolution Diffusion Tensor Imaging of the Cerebellum and Brainstem in Chiari Malformation Type I: Association with Function and Pain.

Chiari Malformation Type I is a congenital neurological condition in which the cerebellar tonsils are displaced into the spinal canal. Common symptoms include pain, motor disturbances, cognitive dysfunction, and anxious-depressive symptomatology. Prior research revealed elevated fractional anisotropy in Chiari patients compared to matched controls using whole-brain diffusion tensor imaging. In the present study, high-resolution diffusion tensor imaging was used to better characterize the white matter tracts of the brainstem and cerebellum affected by Chiari. High-resolution diffusion-weighted images, attention performance data, and symptomatology data were analyzed from 18 Chiari patients and matched healthy controls. Partial brain diffusion-weighted images of the cerebellum and brainstem were processed using an FSL diffusion toolbox pipeline, using the DTIFit, Tract-Based Spatial Statistics, Randomise, and GLM tools. Chiari patients exhibited significantly higher fractional anisotropy in the three cerebellar peduncles and medial lemniscus compared to controls after controlling for attention performance and self-reported pain symptoms. Elevated fractional anisotropy in these regions correlated with attention and pain measures, wherein higher fractional anisotropy was associated with worse attention performance and higher self-reported pain and disability symptoms. This study is the first to resolve white matter abnormalities in the three cerebellar peduncles in Chiari patients. Our findings align with prior observations of increased fractional anisotropy in Chiari patients, though the underlying mechanisms remain debated. We postulate that elevated fractional anisotropy may be the consequence of central pain sensitization and a disrupted neuroinflammatory process in Chiari patients.