202 Diffusion Tensor Imaging Changes with Decompression of Chiari I Malformation.

INTRODUCTION: The compression of the cerebellum is of unclear significance in posterior fossa compression (Chiari I). We studied the diffusion tensor imaging changes (Fractional Anisotropy - FA and Apparent Diffusion Coefficient - ADC) before and after Chiari surgery and correlated findings with clinical and radiological presentation. METHODS: We evaluated MR studies, obtained as part of clinical scans, in 10 patients before and after posterior fossa decompression of Chiari I malformations. Studies included both conventional (structural) MRI and diffusion tensor imaging (DTI). The average DTI parameters of established regions of interest were calculated. Resolution of clinical symptoms was also noted. RESULTS: Nine of 10 patients showed changes from preoperative DTI parameters after decompression. Cerebellar white matter (middle cerebellar peduncle) demonstrated a significant decrease in ADC (pre = 0.77 ± 0.07 (standard deviation), post = 0.72 ± 0.04; T = 3.93, P = 0.003) and trend increase in FA (pre = 0.497 ± 0.079, post = 0.542 ± 0.096 T = −2.18, P = 0.057). All of these patients presented with both radiological and clinical improvement including resolution of syringomyelia, improvement of headaches and other neurological symptoms. All of the patients were able to resume their daily activities. CONCLUSION: Both ADC and FA measurements returned closer to normal expected values in the middle cerebellar peduncle. The increase in FA suggests a normalization of white matter integrity not apparent in conventional imaging. The pre and postoperative diffusion tensor imaging evaluation is a readily available additional tool in the neuroradiological arsenal. It may become a valuable asset in medical decision making and successful management of Chiari I malformation patients. Nevertheless more studies are needed to assess properly its value, correlation with symptoms and outcome, reliability of repeat measurements in non-surgical patients, and any possible clinical application.