Effectiveness of early neuromuscular electrical stimulation on lower extremity functions of stroke patient

Abstract

Although functional electrical stimulation (FES) and transcutaneous electrical nerve stimulation (TENS) has been used for decades, it has been only increasingly applied (in the case of FES) or has just begun to be used (in the case of TENS) in promoting recovery of hemiplegia in stroke rehabilitation over the last decade. Previous studies suffered from certain methodological weakness such as not being randomized clinical trials, or small sample size, or combining subjects with the chronic and acute stroke in the same study. Furthermore, the exponential growth in the understanding of neuroplasticity raises the promising potential of early intervention following brain injury such as stroke. Thus, proper randomized control trials were needed before broad recommendations on the use of FES and TENS in stroke rehabilitation could be formulated. This study was a randomized controlled trial. The hypotheses were that, first, subjects with acute stroke, receiving early FES or TENS plus a standard rehabilitation (SR) program, would have better sensorimotor recovery than those receiving SR alone. Second, the effects of FES were earlier and stronger than that of TENS in improving sensorimotor recovery of stroke subjects. Seventy-seven subjects with acute stroke were recruited and 69 completed the study. After matching for age, gender, type of stroke, side and intensity of paresis, subjects were randomly assigned to 1 of 4 groups: FES (n=13), TENS (n=19), placebo stimulation (n=19) or SR (control, n=18). They were 49-84 years old, 35 males and 34 females, 58 with ischemia and 11 with hemorrhage, 39 with left hemiplegia and 30 with right hemiplegia. All subjects received the same SR program. In the FES group, electrodes were applied to the motor points of the stimulated muscles in the affected lower extremity. The parameters were 0.3 ms pulses, delivered at 30 Hz with an intensity of 20-30 mA. In the TENS group, the electrodes were applied to the acupuncture points in the affected lower extremity. The parameters were 0.2 ms pulses, delivered at 100 Hz with an intensity of 2-3 times the sensory threshold. In the placebo group, the device was the same as in the TENS group, except that the circuit inside the device was disconnected. The stimulation per session lasted for 30 min for FES and 60 min for TENS and placebo stimulation. Treatment was once a day, 5 days a week for 3 weeks. Outcome measurements included (i) proprioception threshold of the knee joint; (ii) spasticity in the affected ankle plantarflexors; (iii) maximum isometric voluntary contraction of the ankle muscles; and (iv) functional mobility in terms of the timed "Up & Go" test. These were measured before treatment (week0), once a week during the 3-week treatment in the hospital, and at week8 post-stroke onset (weekFU). The results showed no significant differences among the groups before treatment. When compared with the other 3 groups, the FES group showed a significant decrease in the affected knee proprioception threshold from week1 to weekFU (P<0.015). There was less percentage increase in the Composite Spasticity Scale (CSS) score in the FES than that in the placebo group at week3 (P<0.05). Muscle strength in the affected side was significantly improved between the FES and the other 3 groups, including increase in the torque and the integrated electromyography (IEMG), and decrease in the EMG co-contraction ratio during ankle dorsi- and plantar-flexion. (P=0.000-0.045). All subjects in the FES group were able to walk within 3 weeks of treatment (P<0.01). When the TENS group was compared with the placebo and control groups, no significant difference was found in the knee proprioception threshold. The percentage increase of the CSS score in the TENS group was significantly less than that in the placebo and control groups at week1 (P<0.05). More subjects in the TENS group had normal plantarflexor resistance at week3 (P=0.002-0.016). The increase in torque and decrease in the EMG co-contraction ratio were significantly greater in the TENS than the control group at week3 and weekFU (P=0.003-0.038). There are 3 main conclusions from the present study. (i) Repeated FES treatment promoted earlier and better sensorimotor recovery of the affected lower extremity and functional mobility in subjects with a first stroke when FES was applied within 2 weeks from stroke onset as opposed to placebo stimulation or SR alone. (ii) Repeated TENS treatment, begun within 2 weeks from stroke onset, significantly slowed the development of spasticity of the affected ankle plantarflexors and improved motor recovery in terms of the increased torque generated by the affected dorsiflexors and decreased antagonist co-contraction when compared with subjects in the placebo and control groups. (iii) The effects of early FES intervention in improving sensorimotor recovery of stroke subjects were earlier and stronger than that of TENS.