Effects of Rhythmic Auditory Stimulation on Gait and on Cortical Activation with Mental Imagery of Walking in Patients with MS

Background: Rhythmic auditory stimulation (RAS) was shown to improve gait in patients with central nervous system disorders. Previous studies conducted by our team demonstrated improvement of gait parameters after a home walking program using RAS in individuals with MS. Patterns of cortical activation on functional MRI (fMRI) were identified in relation to walking and mental imagery of walking, in various populations. To our knowledge, there has been no published study on the immediate effects of RAS on gait and on cortical activation in relation to mental imagery of walking in patients with MS.

Objectives: To measure immediate changes in spatiotemporal (ST) gait parameters with RAS, and to assess changes in cortical activation induced by RAS in MS patients performing mental imagery of walking.

Methods: In this cross-sectional study, subjects with gait disturbance from MS were instructed to perform two series of walks on an electronic gait analysis walkway: 5 walks without RAS (W1), and 5 walks with a fixed sequence (W2: no RAS, RAS at comfortable walking cadence, then 10 and 20% above comfortable walking cadence, then no RAS). A repeated measures ANOVA was used to test for within-subject differences in ST gait parameters. Subjects were scanned while performing walking imagery, with (W+) and without (W-) RAS at their spontaneous walking cadence. For each subject, Student’s t-maps were generated for the W+ and W- conditions. Student’s t-maps were spatially normalized and a voxelwise paired t-test was performed between W+ and W-.

Results: Ten subjects were enrolled: age 51+/-5 years, 60% women, duration of symptoms 17+/-8 years, 60% relapsing MS, Timed 25 Foot Walk 7+/-3 s, 50% used a cane or walker. During W1, stride length (p=0.03 left side, p=0.004 right side) and velocity (p=0.02) improved significantly between the first and second walks. During W2, there was a significant improvement in cadence (p=0.01), and a trend for improvement of velocity (p=0.05) with RAS. Analysis of fMRI data showed increased  activation of the right cerebellum and right insula during W-, while W+ was associated with increased activation in the supplementary motor area, left middle frontal gyrus, and left anterior cingulate, and decreased  activation in the right middle temporal gyrus. The W+/W- comparison showed increased activation in the left superior temporal gyrus and left anterior cingulate in the W+ condition, and  increased activation in the right middle temporal gyrus in the W- condition (p<0.01, corrected for multiple comparisons).

Conclusions: RAS at a tempo above the subject’s spontaneous walking cadence produced an immediate increase in walking cadence. RAS also produced changes in the pattern of cortical activation associated with mental imagery of walking. These results warrant further studies on the mechanism of action and impact of RAS on walking in individuals with MS.