A Follow-up Study of Postoperative DCM Patients Using Diffusion MRI with DTI and NODDI

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to investigate the relationship between spinal cord microstructures and spinal cord dysfunction in degenerative cervical myelopathy (DCM) patients; a follow-up study was carried out using diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI), an advanced diffusion model. SUMMARY OF BACKGROUND DATA: DTI has been used for diagnosis of DCM. Although DTI has advantages of high sensitivity and quantitative features, it is limited by its low specificity for measuring microstructures. METHODS: Fifty-eight postoperative DCM patients with 12 to 14 months of surgical recovery were recruited, as well as 14 healthy volunteers for control group. All DTI and NODDI metrics were measured at the most stenotic levels of patients and at all levels of control group. A t test was used to compare the metrics between patient and control groups, and Spearman correlation was used to test the relationship between the metrics and clinical assessment, modified Japanese Orthopedic Association (mJOA) scores. RESULTS: t test showed that DTI metrics, neurite density Vic, and free water fraction Viso had significant differences between control group and the most stenotic levels in patients. For DTI metrics, fractional anisotropy (FA), radial diffusivity (RD), and mean diffusivity (MD) in patients were significantly correlated with mJOA. For NODDI metrics, only Vic is positively correlated with mJOA. CONCLUSION: The results of t test and correlation with mJOA suggest that DTI and NODDI are valuable for evaluating spinal cord function. Results of NODDI indicate that the reason for FA reduction in DCM may be decreased neurite density, not increased orientation dispersion. LEVEL OF EVIDENCE: 3.