Epidural Spinal Cord Stimulation Reduces Intrinsic Gait Abnormalities in Spinal Muscular Atrophy

Epidural spinal cord stimulation (SCS) has recently been explored in ambulatory individuals with spinal muscular atrophy (SMA), where an increase in muscle strength and endurance with concomitant reduced fatigability was observed. However, the underlying kinematic changes associated with these improvements remain poorly understood. This study aimed to examine whether previously documented improvements following SCS were associated with changes in joint kinematics and movement strategies.

A secondary kinematic analysis of previously collected 6-min walk test (6MWT) data using a 3D motion-capture system and subsequent principal component analysis (PCA) was completed on two ambulatory individuals with SMA. Speed as well as spatio-temporal gait variables and sagittal-plane joint kinematics were defined and compared before and after SCS intervention.

After 4 weeks of SCS, participants walked farther and showed faster, more consistent speeds during the 6MWT. PCA revealed that these improvements were associated with changes in proximal joint velocity (SMA02 mean(L²) = 0.45, SMA03 mean(L²) = 0.54) and proximal joint mobility (SMA 02 mean(L²) = 0.51, SMA03 mean(L²) = 0.40) in both SMA participants. Consistent with these findings, hip range of motion, velocity, and acceleration increased by up to 48%, 44% and 28%, respectively, without evidence of exacerbated compensatory strategies.

SCS may restore access to motor pathways selectively impaired in individuals with SMA. While confirmatory, larger cohort studies are needed, SCS has the potential to reduce intrinsic movement abnormalities and enhance treatment opportunities for SMA.