Dose-Response Relation Between Neuromuscular Electrical Stimulation and Upper-Extremity Function in Patients With Stroke
Background and Purpose— The purpose of our study was to investigate the effects of different doses of neuromuscular electrical stimulation (NMES) on upper-extremity function in acute stroke patients with severe motor deficit.
Methods— Sixty-six acute stroke patients were randomized to 3 groups: high NMES, low NMES, or control. The low-NMES group received 30 minutes of stimulation per day, and the high-NMES group received 60 minutes per day, for 4 weeks. The Fugl-Meyer Motor Assessment Scale, Action Research Arm Test, and Motor Activity Log were used to assess the patients at baseline, 4 weeks, and 12 weeks post baseline (follow-up).
Results— Both NMES groups showed significant improvement on Fugl-Meyer Motor Assessment and Action Research Arm Test scales compared with the control group at week 4 and follow-up. The high-NMES group showed treatment effects similar to those of the low-NMES group.
Conclusions— Higher and lower doses of NMES led to similar improvements in motor function. A minimum of 10 hours of NMES in combination with regular rehabilitation may improve recovery of arm function in stroke patients during the acute stage.
Approximately 40% to 80% of stroke survivors still have moderate to severe arm dysfunction 6 months after stroke.1,2 Past studies have shown that neuromuscular electrical stimulation (NMES) not only facilitates sensorimotor function recovery3–5 but also produces brain plasticity.6,7 Among these studies, the treatment intensity and duration have varied widely (30 minutes to 6 hours per day, for a period of 2 to 12 weeks). Justification for specific treatment parameters has become the focus of current research in the field of stroke rehabilitation.8,9 The purpose of this study was to investigate the effects of different doses of NMES on upper-extremity function in acute stroke patients.
Subjects and Methods
This was an assessor-blinded, block randomized, controlled study. Subjects were recruited from 2 academic medical centers from May 2004 to December 2007. The inclusion criteria were (1) unilateral stroke and onset within 3 months and (2) Brunnstrom stage ≦IV. The exclusion criteria were (1) contraindication for NMES, eg, pacemaker implant, and (2) motor deficit caused by a previous orthopedic or neurologic disorder. Eligible subjects were allocated randomly to the control group, the high-NMES group, or the low-NMES group. The study protocol was approved by the ethics committees.
All subjects received regular inpatient rehabilitation. Treatment groups received an additional 4 weeks of NMES, 5 times per week. Based on local practice experience and previous research, 30 minutes per session was chosen as the low dose and 60 minutes as the high dose. A portable surface neuromuscular stimulator with 2 channels (TENSMED-931) was used to deliver the NMES. The electrodes were placed over the following muscles: extensor digitorum communis, extensor carpi radialis, flexor digitorum communis, supraspinatus, and posterior deltoid. The principles of electrode placement were as follows: (1) When subjects had shoulder subluxation, 1 channel was placed over the supraspinatus and posterior deltoid; (2) when subjects had some visible grasping movement or moderate flexor spasticity (Modified Ashworth Scale >2), electrodes were placed over the extensor digitorum communis and extensor carpi radialis to produce hand opening; and (3) when the hand was completely paralyzed, electrodes were placed over the extensor digitorum communis, extensor carpi radialis, and flexor digitorum communis to produce alternating hand grasping and opening. There were no adverse events, such as burns or skin allergic responses during the study period.
Outcome measures included the upper-extremity motor section of the Fugl-Meyer Motor Assessment Scale, Action Research Arm Test, and Motor Activity Log. The Fugl-Meyer Motor Assessment Scale and Action Research Arm Test were assessed at baseline, after 4 weeks of treatment, and at 2 months’ follow-up. The Motor Activity Log was assessed only at follow-up.
Using the SPSS 13.0 software, 1-way ANOVA, χ2 test, and Kruskal-Wallis H test, we compared the patients’ baseline characteristics. Two-way mixed ANOVA with repeated measures was used to analyze all outcome measures, followed by a post hoc test (Bonferroni test) when the F value was significant. The last-observation-carried-forward method was used as an intention-to-treat method for dealing with missing data. The significance level was set at 0.05. Finally, the effect size (Hedges’ ĝ) of outcome measures was calculated to measure the magnitude of treatment effect.
Sixty-six subjects completed the recruitment and treatment process. No significant difference was found in baseline characteristics among the groups (Tables 1 and 2⇓). Twelve subjects were lost to follow-up because of transportation difficulties (n=10) and relocation (n=2).
Fugl-Meyer Motor Assessment Scale
Two-way mixed ANOVA revealed significant group and time interactions in the Fugl-Meyer Motor Assessment Scale score (F2,63=5.237, P=0.003). Both NMES groups showed significant improvements in total and subscale scores compared with the control group at week 4, and improvement was maintained at follow-up (Table 2). No significant difference was found between the 2 NMES groups. The low-NMES group demonstrated a large effect size (ĝ=0.84, 1.1), and the high-NMES group demonstrated a medium effect size (ĝ=0.68, 0.78) on the Fugl-Meyer Motor Assessment Scale at week 4 and at follow-up.
Action Research Arm Test
Two-way mixed ANOVA revealed significant group and time interactions in the Action Research Arm Test (F2,63=3.943, P=0.016). At follow-up, both NMES groups showed significant improvements (Table 2 and the Figure). Both NMES groups demonstrated medium to large effect sizes (ĝ=0.51, 0.86 for low-NMES group; ĝ=0.45, 0.8 for high-NMES group) at week 4 and at follow-up.
Motor Activity Log
No significant difference was found among the 3 groups at follow-up (Table 2). The low-NMES group demonstrated a medium effect size on the AOU (ĝ=0.65) and QOM (ĝ=0.68). The high-NMES group demonstrated a medium effect size on the AOU (ĝ=0.67) and QOM (ĝ=0.68).
Our results support previous findings that NMES facilitates motor function recovery of affected upper extremities after stroke.3–5 Although both high- and low-NMES groups showed better treatment effects than did the control group, our results did not demonstrate a significant difference between the 2 NMES groups. Increasing the stimulation dose of NMES did not lead to greater improvement. In this study, our high dose was only 30 minutes longer than the low dose per session, a difference that may be insufficient to demonstrate the dose effect. However, we thought that it was impractical to increase the stimulation time beyond 1 hour in common clinical settings. Thus, future studies should consider decreasing the low dose further until the minimal effective clinical dose can be identified.
Another concern was that treatment dose had been defined as the product of stimulation time per session, treatment frequency, or treatment duration.10 Future studies should investigate varying combinations of treatment dose administration for designing intervention programs suitable for clinical practice.
In summary, a minimum of 10 hours of NMES for 4 weeks, combined with regular inpatient rehabilitation, was used to improve motor recovery for subjects with severe motor deficits of the upper extremities. The doses of NMES (10 vs 20 hours) did not affect the outcome measures; hence, the minimal dose remains to be determined.
The authors acknowledge research assistants Yin-Jen Lin, Pei-Chen Lu, and Chia-Jung Tsai for their contribution to this study.
Source of Funding
This study was partially supported by the Bureau of Health Promotion, Department of Health, ROC (Taiwan), through grants DOH93-HP-1114∼DOH94-HP-1114.
- Received November 26, 2009.
- Accepted December 16, 2009.
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