The Evidence...

After researching the use of NMES in children with CP, it became evident to us that there is a multitude of evidence and research for its use. In this post, we aim to provide you with an overview of the current literature available at the present time. Firstly, we will give you an overview of the use of NMES for the upper limb.

A study completed by Kamper, Yasukawa [1] looked at the effects of NMES on upper limb impairment in children with CP, specifically spasticity, coactivation, weakness and heightened passive resistance to wrist rotation. The subjects included nine children with CP from aged five to 15 years all with spastic hemiparesis and impaired voluntary wrist movement with curled fingers.

Subjects were enrolled in a three month NMES program, consisting of two 6-week phases. The first six weeks included stimulation of both wrist flexors and extensors using a pulse duration of 280us, frequency of 35Hz and a pattern of 5s extensors on / 5s extensors off / 5s flexors on / 5s flexors off etc, for 15 minutes. Magnitude was set to maximise muscle contraction at a comfortable level for the subject. Ramp up time was set to 0.5s and ramp down time was zero. This protocol was completed six days per week and subjects were instructed to flex or extend with the corresponding stimulation.

The second six weeks consisted of stimulation of the wrist extensors only with a pattern of 10s on/10s off for 30 minutes. When the subject was able to perform full wrist extension, they were instructed to resist the extension. All other treatment parameters were kept the same.

Outcome measures of voluntary wrist extension, spasticity, passive resistance, strength and co-activation were used to measure results. There were statistically significant increases in voluntary wrist extension (Figure 1) and strength (Figure 4) and also found a significant decrease in co-activation (Figure 5). There were no statistically significant results for spasticity or passive resistance.

Positive results from this study support that NMES can indeed be used for improvement of strength, range of motion and co-activation, however it is important to note that these can be achieved without changes in level of spasticity (which is often a primary treatment goal). It was suggested by Kamper, Yasukawa [1] that increase its effectiveness on spasticity, NMES could be combined with a stretching program which has previously been shown to decrease spasticity in children with CP [2]. A clear limitation of this study is the absence of a control group, so it is difficult to differentiate improvements due to NMES from improvements due to active wrist flexion and extension.

Another interesting study completed by Carmick [3] presented two case studies on the effect of NMES on the upper limb as an adjunct to a dynamic-systems, task-oriented physical therapy program. The first case study included a 19 month old male, diagnosed with left hemiplegia secondary to CP. He began physical therapy at 7 months of age, consisting of task-oriented motor learning activities and various neurodevelopmental techniques to increase sensory awareness. However, by 19 months he was unable to use the left upper limb and therefore had corresponding difficulties when learning to creep and prop on extended elbows. A vibrator was first used on the triceps muscle to elicit a contraction in the left arm, however when removed the arm would collapse.

He was then placed on a NMES program for the triceps. Amplitude was always kept within the child’s comfort, frequency of 30-35Hz, ramp up time of 0.5s on a pattern of 15s on / 25s off for 15-20 minutes, one session per week.

Improvements were seen immediately, with creeping elicited in the first session. Improvements continued even with the NMES removed (Refer to figures below), with the child being able to creep 0.3-0.6m at home each day.

The second case consisted of a 6.7 year old, who had an inability to extend the left wrist, as well as poor functionality of the left hand. He was given NMES treatments using the same parameters in case one to the elbow, wrist and thumb extensors as well as thumb abductors and finger flexors. It took four sessions of NMES before a muscle contraction could be elicited in the wrist extensors. After 10 sessions, the child was able to spontaneously use the hand, and occasionally use the hand to hold objects.

Although this study is limited by a small number of subjects and the lack of a control group, both of the cases provide positive results for the use of NMES in the upper limb to stimulate movement, and increase function, particularly when used as an adjunct to task-oriented physical therapy.

Further research is certainly warranted in this area as the current literature lacks a randomised-controlled trial comparing NMES treatments to a control group. It is therefore difficult to make inferences about the effect of NMES on children with CP, despite the seemingly positive results of the current studies.

The available literature on the use of NMES in the lower limb is also extensive, but not conclusive, and suggests that more research and investigating needs to be done. So really it’s effectiveness in children with CP is still unknown, although it doesn’t take a genius to realise that all treatment should be individualized and therefore all results and affects are also individualized. Common sense and good clinical reasoning should be used when prescribing NMES.

Kerr, McDowell [4] conducted a randomized placebo-controlled trial which investigated the efficacy of NMES and threshold electrical stimulation (TES) in strengthening quadriceps in both legs in children with CP. Sixty children with the mean age of 11yrs were randomly placed into three groups. Of the three groups there was a statistically significant difference between NMES and TES vs. the placebo group for impact of disability at the end of treatment, although only the TES group maintained this difference at the 6 week follow up this can be seen in the table below.

Stackhouse, Binder-Macleod [5] was the first to investigate the use of NMES to increase muscle force production in kids with CP using high force and low repetitions. This preliminary study did find some clinically significant results that included an increase in maximal cross sectional area of the muscle in the children receiving NMES. They also achieved a greater normalized force production as well as an increase in walking speed.

The percentage gains in force production are comparable to that of healthy pre-pubescent children. Stackhouse may have found greater force production in the NMES group due to a more consistent training force; each contraction was not susceptible to voluntary activation. Although voluntary muscle activation was found to be the primary factor that accounts for changes in force production in children with CP after 12 weeks of training.

The use of percutaneous electrodes meant treatment was more tolerable for the children, partly because the implanted electrodes avoided the sensory receptors in the skin and subcutaneous tissue. None of the children experienced any negative responses other than short term muscular soreness after the initial onset of training and after the load was increased.

Over all by ensuring that the contraction was not causing joint pain and through the use of good technique, while being supervised a reasonable level of safety was reached throughout this training protocol. Keeping this in mind it should be noted that in chronic conditions such as CP a little benefit may go a long way for the appropriate patient.

The appropriate application of NMES has been shown to provide some benefits for children with Cerebral Palsy and there is great potential for NMES to be used in conjunction with other forms of Physiotherapy and varying treatment modalities. More research particularly randomized controlled trials need to be conducted before anything definite can be said about NMES as a single modality of treatment. This is the one thing that all the literature has agreed on in regards to the use of NMES in the lower and upper limbs.

 References:

1.            Kamper, D.G., et al., Effects of neuromuscular electrical stimulation treatment of cerebral palsy on potential impairment mechanisms: a pilot study. Pediatr Phys Ther, 2006. 18(1): p. 31-8.

2.            Zhang, L.Q., et al., Intelligent stretching of ankle joints with contracture/spasticity. IEEE Trans Neural Syst Rehabil Eng, 2002. 10(3): p. 149-57.

3.            Carmick, J., Clinical use of neuromuscular electrical stimulation for children with cerebral palsy, Part 2: Upper extremity. Phys Ther, 1993. 73(8): p. 514-22; discussion 523-7.

4.            Kerr, C., et al., Electrical stimulation in cerebral palsy: a randomized controlled trial. Dev Med Child Neurol, 2006. 48(11): p. 870-6.

5.            Stackhouse, S.K., et al., Neuromuscular electrical stimulation versus volitional isometric strength training in children with spastic diplegic cerebral palsy: a preliminary study. Neurorehabil Neural Repair, 2007. 21(6): p. 475-85.