Near-infrared spectroscopy as a quantitative spasticity assessment tool: A systematic review

The purpose of this paper is to systematically review the literature on the use of near-infrared spectroscopy (NIRS) for assessing spasticity. MEDLINE, CINAHL, and EMBASE were searched for human and/or animal studies written in the English language published until November 2018. that used NIRS to examine the hemodynamics and/or metabolism of spastic musculature were included. Of the 35 articles identified, five met the inclusion criteria. Two reviewers independently extracted spasticity outcomes, NIRS instrumentation specifications, and NIRS hemodynamic and metabolic measures from each article. Risk of bias was assessed using the Downs & Black tool for non-randomized studies. Three different models of NIRS devices were used in the five studies. Four studies examined the effects of passive limb movements and one examined active hand movements on NIRS parameters in spastic and non-spastic muscle. Owing to the small number and diverse nature of the studies, statistical comparison was deemed inappropriate. Rather, descriptive comparisons were drawn and levels of evidence were assigned based on the modified Sackett Scale. There is level 4 evidence that NIRS can non-invasively detect and measure differences between spastic and non-spastic muscles in blood volume and oxidative capacity changes over time or in response to interventions, and may correlate with other, established measures of spasticity, such as the Modified Ashworth Scale (MAS) and electromyography (EMG). Future research studies should use a validated definition of spasticity for inclusion criteria, a control group, and standardized NIRS variables.