Who Can Use FES?
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. This will be the case when nerve damage is caused by events such as hip or knee surgery, traumatic accident or peripheral neurophathy due to excess alcohol. It will also be the case if a spinal cord injury is below the level of T12/L1. This is because the spinal cord changes to peripheral nerves at this point. People with Motor Neurone Disease, Polio and Guillain-Barre disease are also not able to use FES because again the peripheral nerves are effected.
FES is however suitable for the following conditions:
Suitability for the Odstock Dropped Foot Stimulator (ODFS)
The selection criteria are essentially the same whether the dropped foot is due to stroke, MS, CP, SCI, head injury or hereditary spastic paraparesis. The criteria are a guide only and exceptions can be made after clinical assessment.
In the case of Parkinson's Decease, the device is used as above but many users may not have a dropped foot, using the device a queuing device to overcome freezing.
Contraindications and precautions
There are few absolute contraindications for using FES but the following should be considered:
1. The safety of FES is not known in pregnancy. No studies have been made.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. FES devices should not be used while driving or operating dangerous machinery.
8. 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.
Referral criteria and treatment protocol Guidlines for referring clinicians