|Functional Electrical Stimulation (FES)
Functional Electrical Stimulation (FES) is a technology for restoring body functions through artificial electrical stimulation of the neuromuscular system.
Specifically, this technology can support the restoration of mobility in paralyzed individuals.
For electrical stimulation to cause a muscle to contract, both the muscle and the nerve that connects it to the spinal cord must be intact.
When a peripheral nerve is damaged, the distal part, i.e. the part furthest from the spinal cord, will degenerate and will not be excitable by electrical stimulation.
Therapeutic stimulation - Therapeutic electrical stimulation is a form of treatment, and is therefore usually carried out under supervision. The benefits form therapeutic electrical stimulation may include: improved muscle tone, strength, reduced spasticity, improved limb blood flow, or a reduction in disuse.
Functional electrical stimulation - FES aims to produce movements or functions which mimic normal voluntary movements and so to restore functions which those movements serve.
The FES devices are under the subject's control and should be available when required during the day's activities at home and elsewhere, rather than being located in a place for 'treatment'. FES equipment must be portable, reliable and easy to use.
Stimulation of the peroneal nerve
||Electrode placement over the peroneal nerve in order to activate the dorsiflexion
Improved gait in a CVA patient
FES is suitable for the following conditions:
Contraindications and precautions (as expressed within the Salisbury FES Clinic web page):
- Multiple Sclerosis
- Spinal Cord injury above T12
- Cerebral palsy
- Traumatic Brain Injury
- Parkinson's syndrome
There are few absolute contraindications for using FES but the following should be considered:
- The safety of FES is not known in pregnancy. No studies have been made.
- There are some rare anecdotal reports that people who have poorly controlled epilepsy have had symptoms increased after using FES. There is no known mechanism for this effect but our advice is that FES should not be used where epilepsy is not well controlled by drugs.
We have however, treated many patients successfully where their epilepsy is well controlled. If FES users are effected they should stop using FES and seek advice.
- People who have a spinal cord injury above T6 may be subject to episodes of autonomic dysreflexia. This is characterised by a rise in blood pressure, elicited by a noxious stimulus bellow the level of the lesion.
FES has been known to cause symptoms of Autonomic dysreflexia in this patient group although symptoms have stopped a soon as the electrical stimulation is removed.
T6 and above SCI should be aware of the possibility and monitor for symptoms. If effected, they should stop using FES and seek advice.
- FES and Cancer. Because FES will increase local blood circulation, it is possible that stimulation in the area of a malignant tuba might increase the rate of metastasising and therefore the spread of the cancer. Electrodes should never be placed over the area of a known tuba.
- Cardiac demand pacemakers that detect the user's heart rate and turn on the pacemaker when the heart rate falls below a predetermined level can be effected by stimulation in certain circumstances. This is because, the pulses from the stimulator may be confused with the ECG from the heart and fool the pacemaker in to thinking the heart is beating faster than it is.
In our practice we consider a pacemaker to be an absolute contraindication to upper limb and shoulder stimulation exercises but that it can be used with caution in lower limb applications. In the latter case, the action of the pacemaker and heart will be checked by a cardiologist while the stimulator is used.
- Poor skin condition can be a problem when self adhesive skin electrodes are used. This is because there is a greater chance of skin irritation.
Electrodes should never be placed over broken skin or over rashes, blisters, spots etc.
If a skin reaction develops, the stimulation must be discontinued until the skin has completely healed.
When starting again use a different type of electrode and/or a stimulator producing a symmetrical biphasic output. A little reddening under the electrode when it is removed is normal and it should fade within a few minutes.
If it is still there the next day then do not use the stimulator and seek advice.
The most important thing to do to avoid a skin reaction is to keep the skin and the electrodes clean by regular washing and regular replacement of the electrodes.
- FES devices should not be used while driving or operating dangerous machinery.
- Avoid handling the electrodes while a stimulator is on. This is to prevent the stimulation affecting other areas of the body. There is a theoretical, but in practice never reported possibility that the electrical stimulation may effect the heart if the current path is directly across the chest. Always remember to turn off the stimulator before you remove the electrodes.
SCI patient performing standing exercises by means of FES ( November 2004, Rehabilitation Hospital of Iasi, Romania)
Important - The stimulators are suitable for ambulatory use.
Patients are first seen at an assessment clinic.
For example, subjects are suitable for FES-based treatment and the use of an ODFS if they have a dropped foot due to an upper motor neurone lesion and are able to walk at least a few metres with appropriate aids or assistance.
The ODFS is fitted over two clinic sessions on consecutive days.
On the first day the user is taught how to apply the device while on the second day their ability to do so is assessed and further training given if necessary. Use of the stimulator is increased gradually over 2 to 3 weeks until it can be used all day.
Follow up is made at 6 weeks, 18 weeks, 45 weeks and 72 weeks from first use and then yearly for as long as the device is used.
Speed walking tests and Physiological Cost Index measurement are used to quantify the treatment outcomes.
Depending of the clinic assessment other stimulators can be recommended within a FES-based treatment.