Background: The spinal cord is a common site of involvement in multiple sclerosis (MS) where pathology contributes substantially to locomotor disability. Previous studies have demonstrated significant correlations between clinical disability and cervical cord atrophy, but not with cord T(2) lesion load. We evaluate cervical cord pathology using, for the first time, quantitative T(1) relaxation time (T(1)), which shows histopathological specificity for tissue damage in the cerebral white matter.
Method: Cervical cord T(1) was compared in 15 MS patients [8 relapsing-remitting (RR), 7 secondary progressive (SP)] and 6 healthy controls, and related to normalised upper cervical cord area (UCCa), cerebral white matter T(1), T(2) lesion load and disability measures including the Expanded Disability Status Scale (EDSS), Ambulation index (AI) and timed 25-foot walk. T1 maps of the brain and cervical cord were acquired using a high-resolution, 3-dimensional fast low-angle shot sequence. Dual-echo sequences were also obtained.
Results: Median cervical cord T(1) [mean (standard deviation)] was significantly greater in RR [854 [28] ms] (p = 0.0006) and SP patients [927 [67] ms] (p < 0.0001) compared with controls [888 [61] ms], and in SP vs. RR patients (p = 0.002). In the overall patient cohort, it correlated significantly with median cerebral white matter T1 (r = 0.7, p = 0.0046), UCCa (r = -0.87, p < 0.0001), but not T2 lesion loads. Both median cervical cord T1 and UCCa (respectively) correlated significantly with the EDSS (r = 0.55, p = 0.03; r = -0.54, p = 0.04), AI (r = 0.77, p = 0.001; r = -0.60, p = 0.02) and timed 25-foot walk (r = 0.56, p = 0.03; r = -0.55, p = 0.04).
Conclusion: Cervical cord T(1) distinguishes between MS subgroups and could also prove a useful surrogate outcome measure in MS. The relation of cervical cord T(1) to cerebral white matter T(1) suggests that cord pathology may be influenced by tissue damage upstream.