Backward Walking Training Induces Structural Changes in the Superior Cerebellar Peduncle: A Pilot Myelin Water Imaging Study

Abstract

Background and Purpose Multiple sclerosis (MS) is a complex neurodegenerative disease that is identifiable by the loss of myelin in the central nervous system (CNS), leading to motor decline. Our lab has shown that backward walking (BW) speed in addition to MRI measures may improve fall prediction for persons with MS (pwMS). Myelin Water Imaging (MWI), a novel technique for assessing the myelin microstructure, has not been examined in relation to BW. This study examines the impact of an 8-week BW training program on the superior cerebellar peduncle (SCP) utilizing MWI, as well as the relation of the change in the SCP to the change in function. Methods Eight individuals with relapsing-remitting MS participated in this pilot study. Participants completed functional tests and a 3T MRI before and after the 8-week intervention, consisting of treadmill and overground BW 1x/week and home exercises 2x/week. Falls were monitored for 6 months after the intervention. The MWI metrics, which included the Myelin Water Fraction (MWF) reflecting myelin content and the geomT2IEW reflecting axon size/packing density, were estimated from the SCP. T-tests were used to examine differences in SCP pre/post and Spearman correlations were used to examine relations among changes in SCP and changes in function. Due to the pilot nature of this study, effect sizes and rho values were prioritized. Results MWF and geomT2IEW values increased after training, with effect sizes of -0.16 and -0.53, respectively. The change in geomT2IEW was strongly correlated with improvements in balance measured with wearable sensors (r=0.61), BW speed (r=0.79), forward walking speed (r=0.52) and prospective falls at 6 months (r=0.46). Discussion Our pilot data suggests that BW training induces both structural (SCP) and functional (balance, gait, falls) changes over 8 weeks and shows potential for future larger-scale studies exploring efficacy. Multiple sclerosis (MS) is a complex neurodegenerative disease that is identifiable by the loss of myelin in the central nervous system (CNS), leading to motor decline. Our lab has shown that backward walking (BW) speed in addition to MRI measures may improve fall prediction for persons with MS (pwMS). Myelin Water Imaging (MWI), a novel technique for assessing the myelin microstructure, has not been examined in relation to BW. This study examines the impact of an 8-week BW training program on the superior cerebellar peduncle (SCP) utilizing MWI, as well as the relation of the change in the SCP to the change in function. Eight individuals with relapsing-remitting MS participated in this pilot study. Participants completed functional tests and a 3T MRI before and after the 8-week intervention, consisting of treadmill and overground BW 1x/week and home exercises 2x/week. Falls were monitored for 6 months after the intervention. The MWI metrics, which included the Myelin Water Fraction (MWF) reflecting myelin content and the geomT2IEW reflecting axon size/packing density, were estimated from the SCP. T-tests were used to examine differences in SCP pre/post and Spearman correlations were used to examine relations among changes in SCP and changes in function. Due to the pilot nature of this study, effect sizes and rho values were prioritized. MWF and geomT2IEW values increased after training, with effect sizes of -0.16 and -0.53, respectively. The change in geomT2IEW was strongly correlated with improvements in balance measured with wearable sensors (r=0.61), BW speed (r=0.79), forward walking speed (r=0.52) and prospective falls at 6 months (r=0.46). Our pilot data suggests that BW training induces both structural (SCP) and functional (balance, gait, falls) changes over 8 weeks and shows potential for future larger-scale studies exploring efficacy.