Evaluation of DTI Parameter Ratios and Diffusion Tensor Tractography Grading in the Diagnosis and Prognosis Prediction of Cervical Spondylotic Myelopathy.

STUDY DESIGN: Prospective cohort.

OBJECTIVE: To explore the correlations between diffusion tensor imaging (DTI) ratios and diffusion tensor tractography (DTT) grading with clinical symptoms and outcomes of cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA: In addition to magnetic resonance imaging (MRI) and compute tomography, DTI may be useful in understanding pathophysiology of spinal cord in earlier stages of the CSM but it may be confounded by age and cervical level, and previous studies had small sample sizes.

METHODS: Controls (n = 36) and patients with CSM (n = 93) underwent magnetic resonance imaging (MRI) and DTI at the Changhai Hospital of Shanghai between September 2011 and March 2013. Apparent diffusion coefficient (ADC), fractional anisotropy (FA) of white matter (WM) and central grey matter (GM) were assessed. Patients were divided into three MRI grades no abnormal signals; increased T2WI; and increased T2WI and low T1WI. DTT images were divided into three grades: no abnormal signals; abnormal local signal cord and disordered fiber tracts; and distortion of the spinal cord and interrupted fiber tracts.

RESULTS: FA and ADC both correlated with age in all 3 bilateral WM funiculi and GM, whereas FA and ADC ratios only showed correlation with age in the ventral funiculus (VF) and central GM. Differences were observed in ADC ratios and FA ratios from different Japanese Orthopedic Association (JOA) score subgroups and JOA recovery subgroups. For the three WM funiculi and GM, correlations between DTI ratios, JOA scores, and JOA recovery rates were consistently higher than those between DTI values, JOA scores, and JOA recovery rates (all P < 0.05). MRI grading was correlated with the JOA scores (r = -0.674, P < 0.001) but not JOA recovery rates (r = -0.197, P = 0.058), while DTT grading was correlated with both JOA scores (r = -0.813, p < 0.001) and JOA recovery rate (r = -0.429, p < 0.001).

CONCLUSION: DTI parameter ratios seemed to be less influenced by age than raw DTI results and could be more valuable than absolute DTI parameters for the evaluation of CSM. DTT grading is more valuable than MRI grading for diagnosis and prognostic prediction in CSM patients.

LEVEL OF EVIDENCE: 3.