Impact of EMG-triggered neuromuscular stimulation of the wrist and finger extensors of the paretic hand after stroke: a systematic review of the literature

OBJECTIVE: To assess whether EMG-triggered neuromuscular electrical stimulation (EMG-NMES) applied to the extensor muscles of the forearm improves hand function after stroke. DESIGN: Systematic review of randomized controlled trials. METHODS: A computer-aided literature search up to June 2006 identified articles comparing EMG-NMES of the upper extremity with usual care. Methodological quality was rated on the Physiotherapy Evidence Database scale (PEDro), and the Hedges' g model was used to calculate the summary effect sizes (SES) using fixed or random models depending on heterogeneity. RESULTS: Eight studies, selected out of 192 hits and presenting 157 patients, were included in quantitative and qualitative analyses. The methodological quality ranged from 2 to 6 points. The meta-analysis revealed non-significant effect sizes in favour of EMG-NMES for reaction time, sustained contraction, dexterity measured with the Box and Block manipulation test, synergism measured with the Fugl-Meyer Motor Assessment Scale and manual dexterity measured with the Action Research Arm test. CONCLUSION: No statistically significant differences in effects were found between EMG-NMES and usual care. Most studies had poor methodological quality, low statistical power and insufficient treatment contrast between experimental and control groups. In addition, all studies except two investigated the effects of EMG-NMES in the chronic phase after stroke, whereas the literature suggests that an early start, within the time window in which functional outcome of the upper limb is not fully defined, is more appropriate.