The Effects of Electrical Stimulation Parameters in Managing Spasticity After Spinal Cord Injury: A Systematic Review

Controversial findings about the effects of neuromuscular electrical stimulation and functional electrical stimulation in managing spasticity have been raised after spinal cord injury. A systematic review was conducted to identify the range of the stimulation parameters that may alleviate spasticity. Three independent reviewers searched Medline (PubMed), web of knowledge, Scopus, Cochrane Central, Virtual Health Library, and Physiotherapy Evidence Database until January 2018. Inclusion criteria were applications of neuromuscular electrical stimulation/functional electrical stimulation on the lower limb muscles, stimulation parameters (frequency, pulse duration, and amplitude of current), and measures of spasticity after spinal cord injury. The primary outcome was spasticity as measured by the Modified Ashworth Scale and the secondary outcome was spasticity assessed by other indirect measures. Twenty-three clinical and nonclinical trials were included with 389 subjects. Neuromuscular electrical stimulation/functional electrical stimulation provided reductions in spasticity by 45%-60% with decrease in electromyography activity and increase in range of motion after spinal cord injury. The identified stimulation parameters were frequency of 20-30 Hz, pulse duration of 300-350 μs, and amplitude of the current greater than 100 mA. Neuromuscular electrical stimulation/functional electrical stimulation provides an effective rehabilitation strategy in managing spasticity. However, a recommendation of the stimulation parameters cannot be accurately assumed because of high variability in the methodology, design, and heterogeneity of the included studies.