Background: Action observation (AO) is a physical rehabilitation approach that facilitates the occurrence of neural plasticity through the activation of the mirror-neural system, promoting motor recovery in people with stroke.
Objectives: To assess whether action observation enhances motor function and upper limb motor performance and cortical activation in people with stroke.
Search methods: We searched the Cochrane Stroke Group Trials Register (last searched 4 September 2017), the Central Register of Controlled Trials (24 October 2017), MEDLINE (1946 to 24 October 2017), Embase (1974 to 24 October 2017) and five additional databases. We also searched trial registries and reference lists.
Selection criteria: Randomized controlled trials (RCTs) of AO, alone or associated with physical practice in adults after stroke. The primary outcome was upper limb motor function. Secondary outcomes included dependence on activities of daily living (ADL), motor performance, cortical activation, quality of life, and adverse effects.
Data collection and analysis: Two review authors independently selected trials according to the pre-defined inclusion criteria, extracted data, assessed risk of bias, and applied the GRADE approach to assess the quality of the evidence. The reviews authors contacted trial authors for clarification and missing information.
Main results: We included 12 trials involving 478 individuals. A number of trials showed a high risk of bias and others an unclear risk of bias due to poor reporting. The quality of the evidence was 'low' for most of the outcomes and 'moderate' for hand function, according to the GRADE system. In most of the studies, AO was followed by some form of physical activity.
Primary outcome: the impact of AO on arm function showed a small significant effect (standardized mean difference (SMD) 0.36, 95% CI 0.13 to 0.60; 8 studies; 314 participants; low-quality evidence); and a large significant effect (mean difference (MD) 2.90, 95% CI 1.13 to 4.66; 3 studies; 132 participants; moderate-quality evidence) on hand function.
Secondary outcomes: there was a large significant effect for ADL outcome (SMD 0.86, 95% CI 0.11 to 1.61; 4 studies, 226 participants; low-quality evidence). We were unable to pool other secondary outcomes to extract the evidence. Only two studies reported adverse effects without significant adverse AO events.
Authors' conclusions: We found evidence that AO is beneficial in improving upper limb motor function and dependence in activities of daily living (ADL) in people with stroke, when compared with any control group; however, we considered the quality of the evidence to be low. We considered the effect of AO on hand function to be large, but it does not appear to be clinically relevant, although we considered the quality of the evidence as moderate. As such, our confidence in the effect estimate is limited because it will likely change with future research.