Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression

Objective: To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings. Materials and Methods: A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD${\cap}$FA (considered positive when both the MD and FA results were positive), LD${\cap}$FA (considered positive when both the LD and FA results were positive), and RD${\cap}$FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard. Results: The MD, LD, and RD cut-off values were $1.079{\times}10^{-3}$, $1.719{\times}10^{-3}$, and $0.749{\times}10^{-3}mm^2/sec$, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD${\cap}$FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD${\cap}$FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD${\cap}$FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD${\cap}$FA (p = 0.003), FA and LD${\cap}$FA (p < 0.001), FA and RD${\cap}$FA (p < 0.001), MD and LD${\cap}$FA (p = 0.024) and MD and RD${\cap}$FA (p = 0.024). Conclusion: Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.