Magnetization transfer ratio of the spinal cord in multiple sclerosis: Relationship to atrophy and neurologic disability

The authors compare the spinal cord magnetization transfer ratio (MTR) of m ultiple sclerosis (MS) patients to healthy volunteers, relate MTR to spinal cord atrophy, and relate these and other magnetic resonance (MR) imaging p arameters to disability. Sixty-five patients with MS (14 relapsing remittin g [RR], 34 secondary progressive [SP], and 17 primary progressive [PP] MS), and 9 healthy volunteers were studied using MR at 1.0 T. Disability of the patients was assessed using the expanded disability status scale (EDSS). M agnetic resonance parameters were upper spinal cord MTR, number of focal sp inal lesions, presence of diffuse abnormalities, and spinal cord cross-sect ional area (CSA). Correlations were assessed using Spearman's rank correlat ion coefficient (r). Magnetization transfer ratio was higher in the control s (median, 33%; range, 30%-38%) than in patients with MS (median, 30%; rang e, 16-36; p < 0.05). In patients with MS, EDSS correlated with spinal cord MTR, albeit weakly (r = -0.25, p < 0.05). Correlation between EDSS and spin al cord CSA was better (SRCC = -0.40, p < 0.01). No correlation was found b etween MTR and CSA (r = 0.1, p = 0.4). Combining MTR with spinal cord CSA i mproved correlation with EDSS (r = -0.46, p < 0.001), suggesting an indepen dent correlation between disability and these 2 MR parameters. Expanded dis ability status scale scores were higher in patients who had diffuse spinal cord abnormality regardless of focal lesions (median, 6; range, 1.5-7.5) th an in patients without diffuse abnormalities (median, 3.5; range, 0-8; p < 0.01). CSA was lower in patients with diffuse spinal cord abnormality (medi an, 62; range, 46-89 2) than in patients without diffuse abnormalities (med ian, mm 73; range, 47-89 mm(2); p < 0.01). MTR was slightly lower in patien ts with diffuse spinal cord abnormalities (median, 29; range, 21%-33%) than in patients without diffuse abnormalties (median, 31, range, 16-36; t-test , p < 0.05).