Quantitative Assessment of the Cervical Spinal Cord Damage in Neuromyelitis Optica Using Diffusion Tensor Imaging at 3 Tesla

Purpose: To investigate whether quantitative MRI measures of cervical spinal cord white matter (WM) using diffusion tensor imaging (DTI) in neuromyelitis optica (NMO) differed from controls and correlated with clinical disability. Materials and Methods: Ten referred patients and 12 healthy volunteers were imaged on a 3 Tesla scanner and patients were clinically assessed on the Expanded Disability Status Scale (EDSS). Two raters quantified DTI-derived indices from all participants, including fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (lambda[ parallel]) and perpendicular diffusivity (lambda[perpendicular]) at C1-C6 for lateral and dorsal columns. After the inter-rater reliability test, univariate correlations between DTI measures and disability were assessed using the Spearman's rho correlation coefficient. Multiple regression analysis was performed to investigate which DTI measures independently correlated with the clinical score. Results: Statistical test results indicated high reliability of all DTI measurements between two raters. NMO patients showed reduced FA, increased MD and lambda[perpendicular] compared with controls while lambda[ parallel] did not show any significant difference. The former three DTI metrics also showed significant correlations with disability scores, and especially FA was found to be sensitive to mild NMO (EDSS <= 3) Conclusion: FA is a potentially useful quantitative biomarker of otherwise normal appearing WM damage in NMO. Such damage is associated with clinical disability.