Cerebral palsy (CP) is a physical disability that affects movement and posture. It is permanent and life-long. It is caused by damage to the developing brain which can either occur during pregnancy or just after birth. The effects on muscles (including control, co-ordination, tone and strength) as well as balance and posture means that mobility is affected.
Children and adolescents with cerebral palsy often have problems with their ability to walk. Weak leg muscles make it difficult or even impossible for the children and youth to control how they move their ankle and toes. Without this ability, tripping and falling is inevitable making walking very difficult. This can severely impact daily life, limiting the ability to walk safely. Current treatments to improve walking for children with hemiplegia include the use of botulinum toxin type A (Botox), physiotherapy and the use of ankle foot orthoses (AFOs). Though the use of AFOs can improve how a child walks, it can also potentially limit how a child learns to balance and calf muscle development. For this reason, it is worth exploring other potential treatments that can support walking in children with hemiplegia.
Technology is always evolving and this presents as an exciting opportunity to find new and innovative ways to provide treatments to children and adolescents with physical disabilities. There are devices that can be strapped to the leg that provide electrical impulses to lift the toes up at the exact time when walking to prevent trips and falls.
Muscle Electrical Stimulation is a therapy method that can be used to improve walking for children with unilateral cerebral palsy (also known as hemiplegia). With this method, pads are placed on the skin directly over the target muscles. An electrical current is then used through the pads to get the muscle to contract or flex. This takes the movement out of the control of the child as the device is used instead to get the muscle to flex. In the case of walking, pads are placed on the front of the leg, directly over the muscles that lift the toes up when walking. When the device is turned on, it sends the electrical current to the muscle to flex at the exact time the person is about to take a step. This means the person can take a step without dragging their toes, tripping or falling.
In this way, the muscle electrical stimulation is acting like an orthotic. This can often be called the Orthotic Effect. Given that the muscle is stimulated with each and every step, it can affect how new skills are learnt. This is called the Therapeutic Effect.
The Walk Study
Over the past 4 years, with the support of the Perth Children’s Hospital Foundation, our research team has conducted and published numerous studies to establish the effect of muscle electrical stimulation on a range of outcomes in children with physical disabilities. We have shown that it is effective in improving walking ability, strength, balance and even muscle size. It was well tolerated and described to be preferable to braces.
Our study involved 32 children with unilateral cerebral palsy. The average age of children in the study was 10 years and 8 months. The average use of time using the muscle electrical stimulation device was 6.2 hours as most children used the device during their school day.
The study was a randomised controlled trial which means that half of the children were randomly allocated to the group that were asked to wear the device everyday for 8 weeks. The other half were asked to continue with whatever it is that they usually do. This method of research enables researchers to see if one method of treatment is any better or worse than the other.
The Walk Study
Electrical Stimulation and Walking
What did our studies show?
Our studies demonstrated that you can improve how a child with cerebral palsy (unilateral or hemiplegia) walks with muscle electrical stimulation. This can be seen by:
- How much the ankle flexes up when taking a step and the ability to strike the ground with the heel first (as opposed to the toes).
- The length of each step is also improved to match the other leg giving a more symmetrical or even way of walking.
These improvements were only seen when the muscle electrical stimulation device was worn. When it was taken off, these effects were no longer seen. This means that Muscle Electrical Stimulation can provide a true Orthotic Effect. This is demonstrated graphically in Figure 1.
When the device was taken off we saw improvements in balancing skills. These skills include standing on one leg as well as negotiating obstacles and steps. This suggests that new skills can be learnt as a result of using the muscle electrical stimulation device. It is therefore possible to see a Therapeutic Effect. This is evident with the improved scores on the Community Mobility Balance Scale as shown in Figure 2.
Electrical stimulation and walking
Electrical Stimulation and Muscles
What did our studies show?
All children in the study had an MRI (Magnetic Resonance Imaging) taken at baseline, post treatment and follow up. The MRI enables us to see a cross section of the muscles along the length of the leg. It is a great way to measure muscle size - it is in fact the gold standard of measuring muscle. Using specialised software, we were able to measure each muscle in the leg. Consistent with all the research already out there, we found that at baseline, the muscles on the side that was most affected were much smaller than the other leg. Have a look at the MRI picture below. The cross section of the leg on the left side is smaller in diameter. There is also more white space which indicates there are less muscle fibres meaning that it is harder for the muscle to generate force when it flexes.
After the children used the Muscle Electrical Stimulation for 8 weeks, there were some significant improvements in muscle size. The entire muscle group at the front of the leg (anterior compartment) had a sizable increase which means that the muscle grew during the treatment. What we didn’t expect to find was that the calf muscle - gastrocnemius (both the medial and lateral parts) also grew in size. We concluded that the muscle grew because the child was able to push off more effectively when walking, allowing the muscle to contract or flex. This could also be because children stopped using their ankle foot orthoses which usually blocks the ability to push off with their ankle. The graphs below show the mean symmetry ratio values where a ratio value of 1 means that the muscles are exactly the same size on the left and right. The medial and lateral gastrocnemius muscles became more symmetrical in size after treatment and even sustained this improvement at follow up suggesting a carry over effect. Tibialis anterior and the rest of the anterior compartment also became more symmetrical after treatment but this was not maintained at follow up suggesting that electrical stimulation needs to remain on for this muscle to keep its size.
Electrical Stimulation and Muscles
Muscles Electrical Stimulation and Participation
The effects of muscle electrical stimulation can mean different things to different people. It is important to know this because despite the results we got from the study, how it works for each person and their family is individual as must be reviewed on a case by case basis.
For the 16 children who were asked to use the device, they reported some changes which revealed 5 main themes.
- Improved running and walking (reported by 13 children)
- Improved comfort with more options to wear different shoes (reported by 6 children). Some of the comments included “the device means less blisters on my feet, easier to put on shoes” and “her dad got her ‘girlie’ shoes and they stay on her feet - really pleased”
- Reduction in trips and falls (reported by 4 children)
- Improved confidence (reported by 4 children)
- Increased foot awareness (reported by 2 children). Some of the comments included “feel more aware of your foot placement when wearing the device” and “I can feel when it raises my toes when walking”.
There were also some disadvantages to using the device. Two children reported that they had problems with the size of the device. This meant that after strapping the device to the leg just below the knee, it was hard to put clothing over it. Pants were hard to wear and in winter this can be a problem. Another problem was that the device that was used (Innovative Neurotronics: Walk Aide) seemed to “fall apart quite often”.
After the study, three of the participants opted not to continue using the device because they had problems with:
- Accurate placement of the device: It is important that the cuff that the device sits on is placed in exactly the same spot each time so that the right muscle is activated. For some children, this was very challenging.
- Bulkiness of the device
- Problems with wearing school uniforms particular when it involves stockings or leggings.
- Difficult in attaining a good fit owing to the cuff sliding down the leg during walking.
There were also some reports that we as researchers weren’t expecting. Below is a quotation from a 16 year old girl who wore the device. She reports changes on a very personal level which were incredibly meaningful for her.
“Although compared to many other cases, my CP is quite mild, it has had quite an effect on me over the years; mentally, physically and emotionally…. To be honest I wasn't very keen on it in the beginning; I felt like it added to the things that made me different… but as the study progressed it quickly became the thing that drew me closer to my peers. Emotionally, I struggled with feeling different or out of place; having to wear splints or orthotics, but through the use of the Walk Aide, I began to feel more confident and enthusiastic to do the things I had to do to maintain the physical effects of the Walk Aide. The Walk Aide for me, reduced, in fact eliminated my pain (foot, leg and low back), boosted my confidence, gave me the ability to wear shoes like thongs in summer (one of my goals), increased my energy levels, and gave me the ability to walk long periods of time without growing weak or sore.”
Who are the most appropriate candidates for a muscle electrical stimulation trial?
Based on our research, the most suitable candidates for using muscle electrical stimulation when walking are:
- Children and young people with cerebral palsy who can walk independently in the community without the assistance of any equipment but have difficulties with lifting their foot up on one side causing them to drag their toes or frequently trip and fall.
- Willing to use a device under their knee during the day when they are walking.
The potential benefits for suitable candidates include:
- Improved STRENGTH in the muscle that lifts the toes up when walking.
- Reduced SPASTICITY in the calf muscle
- Improved MUSCLE SIZE in the muscle under the knee.
- Improved WALKING PATTERN i.e. more even and symmetrical.
- Improved BALANCE when walking around the school and the community.
- Less TRIPS and FALLS when walking around the school and the community.
Would you like more information?
The articles that provide this evidence are:
- Pool, D., Blackmore, A. M., Bear, N., & Valentine, J. (2014). Effects of Short-Term Daily Community Walk Aide Use on Children With Unilateral Spastic Cerebral Palsy. Pediatric Physical Therapy, 26(3), 308–317. doi: 10.1097/PEP/0000000000000057
- Pool, D., Valentine J., Blackmore A.Marie., Colegate, J., Bear N., Stannage, K., & Elliott C. (2015). Daily functional electrical stimulation during everyday walking activities improves performance and satisfaction in children with unilateral spastic cerebral palsy: a randomised controlled trial. Archives of Physiotherapy, 5(5), doi:10.1186/s40945-015-0005-x.
- Pool, D., Elliott, C., Bear, N., Donnelly, C.J., Davis, C., Stannage K., & Valentine, J. Forthcoming. Neuromuscular electrical stimulation assisted gait increases muscle strength and volume in children with unilateral spastic cerebral palsy: a randomised controlled trial. Developmental Medicine and Child Neurology.
- Pool, D., Valentine, J., Donnelly, C.J., Bear, N., Elliott C., Stannage, K. Forthcoming. The orthotic and therapeutic effect following daily community applied functional electrical stimulation in children with unilateral spastic cerebral palsy: a randomised controlled trial. BMC Pediatrics.