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 (NMES) and functional electrical stimulation (FES) in managing spasticity have been raised after spinal cord injury (SCI). 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 NMES/FES on the lower extremity muscles, stimulation parameters (frequency, pulse duration and amplitude of current) and measures of spasticity after SCI. 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 non-clinical trials were included with 389 subjects. NMES/FES provided reductions in spasticity by 45-60% with decrease in electromyography activity and increase in range of motion after SCI. The identified stimulation parameters were frequency of 20-30Hz, pulse duration of 300-350 μs and amplitude of the current > 100 mA. NMES/FES provides an effective rehabilitation strategy in managing spasticity. However, a recommendation of the stimulation parameters cannot be accurately assumed due to high variability in the methodology, design and heterogeneity of the included studies.