The effect of intramuscular interferon beta-1a on spinal cord volume in relapsing-remitting multiple sclerosis.

Background: Spinal cord atrophy occurs early in multiple sclerosis (MS) and impacts disability. The therapeutic effect of interferon beta-1a (IFNβ-1a) on spinal cord atrophy in patients with relapsing-remitting (RR) MS has not been explored.

Methods: We retrospectively identified 16 consecutive patients receiving weekly intramuscular IFNβ-1a for 2 years [baseline age (mean ± SD) 47.7 ± 7.5 years, Expanded Disability Status Scale score median (range) 1.5 (0-2.5), timed 25-foot walk 4.6 ± 0.7 seconds; time on treatment 68.3 ± 59.9 months] and 11 sex- and age-matched normal controls (NC). The spinal cord was imaged at baseline, 1 and 2 years later with 3T MRI. C1-C5 spinal cord volume was measured by an active surface method, from which normalized spinal cord area (SCA) was calculated.

Results: SCA showed no change in the MS or NC group over 2 years [mean annualized difference (95 % CI) MS: -0.604 mm (-1.352, 0.144), p = 0.106; NC: -0.360 mm (-1.576, 0.855), p = 0.524]. Between group analysis indicated no differences in on-study SCA change [MS vs. NC; year 1 vs. baseline, mean annualized difference (95 % CI) 0.400 mm (-3.350, 2.549), p = 0.780; year 2 vs. year 1: -1.196 mm (-0.875, 3.266), p = 0.245; year 2 vs. baseline -0.243 mm (-1.120, 1.607), p = 0.712].

Conclusion: Established IFNβ-1a therapy was not associated with ongoing spinal cord atrophy or any difference in the rate of spinal cord volume change in RRMS compared to NC over 2 years. These results may reflect a treatment effect. However, due to sample size and study design, these results should be considered preliminary and await confirmation.