New diffusion metrics for spondylotic myelopathy at an early clinical stage

OBJECTIVES: To investigate the use of root mean square displacement (RMSD) and mean diffusional kurtosis (DK) metrics of q-space imaging data to estimate spinal cord compression in patients with early cervical spondylosis. METHODS: We studied 50 consecutive patients at our institution (22 male, 28 female; mean age 58 years; age range 20–86 years) who had clinical signs and symptoms suggestive of early clinical stage cervical myelopathy. After conventional magnetic resonance (MR) imaging, diffusion tensor and q-space image data were acquired using 3-T MR imaging. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), RMSD and mean DK values were calculated and compared between compressed and uncompressed spinal cords. RESULTS: FA and mean DK values were significantly lower and RMSD was significantly higher (P = 0.0060, 0.0020 and 0.0062, respectively; Mann–Whitney U test with the Bonferroni correction) in compressed spinal cords than in uncompressed cords. ADC was also higher in compressed cords, but this difference was not statistically significant. CONCLUSIONS: In the evaluation of spinal cord damage in early cervical spondylosis, mean DK and RMSD values in the spinal cord may be highly sensitive indicators of microstructural change and damage. KEY POINTS: • Absolute surgical indications for cervical spondylosis with myelopathy remain to be established. • Diffusion tensor MRI shows abnormalities in normal-appearing but compressed spinal cord. • Non-Gaussian diffusion analysis is highly sensitive in revealing spinal cord damage.