Transcutaneous electrical spinal cord stimulation increased target-specific muscle strength and locomotion in chronic spinal cord injury

Abstract

Background: The recovery of locomotion is greatly prioritized, and neuromodulation has been emerging as a promising approach in recent times. Study design: Single-subject research design. Settings: A laboratory at The Hong Kong Polytechnic University. Objectives: To investigate the effects of augmenting activity-based therapy (ABT) to transcutaneous electrical spinal cord stimulation (TSCS) on enhancing specific lower limb muscle strength and improving locomotor ability in an individual with chronic incomplete spinal cord injury (iSCI). Methods: An individual with iSCI underwent two phases of treatment, ABT alone followed by combined ABT+TSCS, each for a period of 10 weeks. The TSCS stimulated T10-T11 and T12-L1 segments with a frequency of 30 Hz at an intensity between 105 mA and 130 mA. Manual muscle testing, 6 min walk test (6MWT), and surface electromyography (EMG) responses of specific lower limb muscles were measured. Additionally, spasticity and sensorimotor examinations were conducted every two weeks, while pain tolerance was recorded after each treatment session. Results: After the ABT+TSCS treatment, there was an increase in overall muscle strength grading (from 1.8 ± 0.3 to 2.2 ± 0.6 out of 5.0). The 6MWT showed a greater increase in walking distance (3.5 m to 10 m) after combined treatment than ABT alone. In addition, the EMG response of the anterior rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior after ABT+TSCS increased more than after ABT alone. The spasticity grade was reduced (from 0.8 ± 0.7 to 0.5 ± 0.6) whereas the average lower limb motor score increased from 17 to 23 points. No adverse effects were reported. Conclusions: ABT+TSCS increased the target-specific lower limb muscle strength and walking ability more than ABT alone in an individual with chronic iSCI.