Because amyotrophic lateral sclerosis (ALS) is a chronic disorder in which there may be periods of spasticity and muscle weakness and then a long term period of mower motor neuron degeneration and “flaccid paralysis,” the indications for and the application of electrical stimulation (ES) will vary with the symptoms and functional limitations. ES may be helpful in the management of spasticity, with resulting improvement in muscle performance, urinary incontinence, breathing and a reduction in pain. Applications that involve the use of skin electrodes may be accomplished with a variety of commercially available electrical stimulation devices that are small, battery powered and inexpensive. Implantable electrical stimulation technology would be selected by the surgeon.
Management Of Spasticity
ES has been demonstrated to reduce or eliminate interfering spasticity, or involuntary muscle activity, in ALS. The involuntary muscle activity may take the form of spontaneous muscle contractions or it may occur when voluntary movement is initiated. A variety of ES protocols have been employed. Some investigators and clinicians have used inexpensive portable stimulators and skin electrodes (placed on the spastic muscles, or over the muscles that work against the spastic muscles or on areas of skin that receive the same nerve supply as the spastic muscles). The intensity of ES may be minimal, with only a tingling sensation felt by the user. In other protocols, the intensity of ES is increased to assist with joint movement. The intensity of ES should never cause discomfort. Other clinicians have surgically placed electrodes over the dorsal columns of the spinal cord or over peripheral nerve. Stimulation protocols varied from one to two hours each day to intermittent use all day long, as needed.
As a result of ES, spasticity has been reduced, pain was less, bowel and bladder function improved and voluntary use of the hand increased as a result of reduction in interfering spasticity.
Maintaining Or Improving Joint Range Of Motion
For the ALS individual who has sufficient nerve supply to the muscles, ES can be used to move the joint to the end of the available range or it can be combined with the patient’s exercise to be sure the patient is going to the end of the range and stretching just a bit. Electrical stimulation for this purpose has advantages over vigorous manual range of motion including the use of the individual’s muscles to gain the range in a gentle manner without traumatizing the tissues and it can be done several times during the day as part of a home program.
When spasticity has contributed to the limitation of joint motion, the movement may improve remarkably as ES helps to reduce the spasticity.
Among the advantages of improved joint range of motion are greater ease of positioning and reduced risk for development of pressure sores. For the individual who has the ability to walk, improved range will reduce the energy expenditure of standing and walking which should translate into less fatigue.
Improving Muscle “Strength” Or Performance
When interfering spasticity is reduced or eliminated, muscles may appear to be stronger in the absence of actual change in the muscle properties. In addition, ES may improve the timing or recruitment of muscles so that muscles exert force in a more useful and coordinated manner. Exercise home programs, with ES added to voluntary effort, can be designed to improve muscle force production and fatigue resistance for the individual with adequate nerve supply to the muscles.
Reducing The Risk Of Respiratory Infection
While most people with ALS who can walk are not likely to have serious impairment of their respiratory muscle function, those in a wheelchair with decreased arm and trunk activity are at risk for respiratory compromise and infection. One of the most serious problems is the reduction in coughing ability and ES may be useful in contracting the abdominal muscles to assist in coughing and keeping the airway clean. Reduction of spasticity by ES may improve breathing and coughing by allowing more coordination of the muscles of inspiration and expiration. Again, there must be an adequate nerve supply to the muscles for ES to be successful in these endeavors.
Minimizing The Risk Of Pressure Sores And Treating Skin Lesions
Among the many factors that contribute to pressure sores are spasticity, joint contractures, muscle paralysis and poorly fitting wheelchairs. ES may reduce the risk by reducing the involuntary movements in spasticity, by improving joint range of motion, and by increasing the bulk of muscles that cushion the bony prominences and so distribute pressures more evenly over the skin.
Once a pressure sore has occurred, ES may be helpful in speeding the healing process. While most of the research in this area has been done in spinal cord injury or diabetes, the findings are applicable to ALS. Possible mechanisms include improving the oxygen supply to the skin and the muscle in the area of the sore, improving the rate of deposition of connective tissue, or scar, and minimizing the infection in the wound. The chance of healing is, of course, better if the pressure sore is a partial thickness lesion, meaning that only the more superficial layers of the skin are missing. In this case, the skin can grow from the base or bed of the dermis, similar to the way grass grows after mowing. If the sore is deep enough to go through the skin, it must heal in from the sides and surgery is often needed. If there is infection underlying the skin and in the exposed bone, surgical intervention is required to clean the area and to graft skin and sometimes muscle over the bony prominences. After wound closure, the mechanical integrity of the skin will not return to normal and it will be necessary to continue routine skin checks and to use custom seating devices for pressure relief as needed.
Successful ES protocols have included daily stimulation for a total time of two or more hours. Some investigators have employed a very low intensity, direct current. Others have used a pulsatile current and created a muscle contraction in the area of the pressure sore. Electrodes may be placed adjacent to the wound or one of the electrodes may be placed in the wound. In the latter case, an electroconductive dressing is used as the electrode.
Contributor: J.M. Campbell, Ph.D., P.T.