Approximately one in five survivors of poliomyelitis will experience a recurrence of muscle weakness and fatigue in the form of post-polio syndrome. Patients most commonly present to physicians after noticing a marked change in their ability to perform relatively simple physical activities. A properly designed exercise program will aid in replenishing lost strength in affected muscles.
There is little that will strike fear into the heart of a polio survivor as much as a feeling that the dreaded symptoms of poliomyelitis are returning. In approximately 20% of individuals who had polio during the epidemics of the 1940's and 1950's, however, this fear is returning, as these polio survivors experience post-polio syndrome (PPS).
The characteristic features of PPS are the presence of gradually increasing muscle weakness and fatigue, felt in the same muscles that had been affected by polio and had recovered, associated with a sensation of generalized fatigue. Muscle and joint pain are also common complaints and should be considered as possibly being caused by PPS if other symptoms are present.
Muscle Weakness and fatigue
Two presentations of muscle weakness can be encountered. The first is a weakness which has been present since polio and has caused a significant decrease in limb function after recovery from acute poliomyelitis. This is the weakness that caused a perpetual limp, or inability to perform the activities expected from a normally functioning arm or leg because of only partial recovery of muscle function after polio. In this type of infirmity, the patient has noted a significant increase in the weakness over the past two to three years, rendering the corresponding limb almost useless.
The second type of weakness appears from 25 to 40 years after acute polio, after a period of virtually normal muscle function during that time period. This weakness always occurs in the same muscles that had been paralyzed and then had recovered from acute polio.
The most common motivation of the patient to seek help is the marked change in ability to perform relatively simple physical activities. An individual who previously was able to walk kilometres without trouble is now limited to walking only one to two city blocks, after which he must stop because of the rapid onset of inability to contract the leg muscle (weakness) and the inability to continue this physical activity because of perceived fatigue of the muscle. These are two separate phenomena which appear in the same previously paralyzed muscle.
The same events occur when the patient attempts to climb stairs. Where previously he was able to climb a few flights of stairs without difficulty, he now needs the help of a railing to permit the slow ascent of the stairs (weakness) and the number of stairs is limited to usually no more than one flight (fatigue) because of inability to maintain the repeated contractions that are needed to perform this task.
This combination of weakness and fatigue of previously paralyzed muscles is accompanied by a sensation of generalized fatigue. This phenomenon usually comes on between noon and 3 p.m. daily and is severe enough to force the patient to rest during the early afternoon so as to permit him to continue to function through the rest of the day without requiring sleep by early evening.
Muscle and joint pain
This is the least frequent complaint among polio survivors, but when present, this pain is extremely disabling. There are two main reasons for this symptom: Excessive stress on joints that underlie weakened muscles, or as a result of neurogenic reasons which cause a more causalgic type of pain.
If the history of onset of weakness is characterized in the muscles that were initially affected by polio either by ongoing muscle weakness since the onset of polio or by recurrent weakness after a latency period of 25 to 40 years after recovery, clinical verification of weakness is necessary. Muscle testing will reveal the presence of clinical lack of strength in these muscles.
In addition, other reasons, such as radiculopathy or other muscular or other muscular or neurologic disorders, must be ruled out as a cause of weakness.
Confirmation of the diagnosis and differentiation between the two major causes of feebleness is achieved by electromyography (EMG). When all muscles that have been identified on clinical examination as being weakened are subjected to EMG, the presence of previously existing polio will be confirmed by the finding of large-amplitude polyphasic potentials appearing on voluntary movement in the muscles that are being examined.
In addition, when the muscles are initially subjected to needle examination, the presence of insertional activity identifies muscles that are weakened as a result of incomplete recovery from polio. These are the muscles that have had weakness present since recovery from polio. However, muscles which demonstrate recurrence of weakness after a period of 25 to 40 years demonstrate an absence or marked decrease of insertional activity.
It has been demonstrated that when subjective weakness is identified, the number of available motor units in the weakened muscle has been reduced by 50%. In post-polio muscle weakness, the reduction of the number of motor units to 50% is achieved in two ways.
In weakness resulting from incomplete recovery from acute polio, the number of motor units that is available for function is reduced after recovery. The normal process of motor unit reduction exerts its influence over 25 to 40 years, as there is a slow but steady decline of the number of available motor units to below 50%, resulting in severe weakness and dysfunction.
The second type of weakness occurs as a result of the development of abnormal neuromuscular junctions formed between the reinnervating nerve sprouts and the previously paralyzed muscle fibers. This development occurs as part of the recovery process following acute polio. These abnormal junctions appear to be unable to maintain their function and deteriorate more rapidly than normal junctions, with the result that they disappear at a rate of 2% to 5% per year. The loss to below 50% of available motor units is achieved within 20 to 40 years, leading to the presence of clinical weakness. This latter phenomenon identifies the post-polio muscle.
EMG needle studies are used to differentiate between these two types of frailty. Normal insertional activity is seen in incompletely recovered muscles, while absent or markedly reduced insertional activity is encountered in the post-polio muscle, when the EMG needle is inserted into the resting muscle.
The etiology of the generalized fatigue noted in these patients is not yet totally understood. The finding of chronic inflammatory changes in the spinal cords of patients having symptoms of PPS but who died for unrelated reasons may shed some light as to the reason for this ongoing and debilitating fatigue.
In the presence of weakness caused by incomplete recovery, regular strengthening exercises are prescribed. Since these are essentially normal muscles, except for the presence of a decreased number of motor units, exercise can be implemented without regard for fatigue.
The literature is replete with the documentation that some muscles in post-polio syndrome become weaker and atrophy when they are fatigued during exercise. These muscles are the ones that are designated as post-polio muscles and are identified as such by EMG. They may be subjected to strengthening exercises, but this exercise must be designed in such a way as to avoid fatigue. The term "non-fatiguing strengthening exercises" (NFSE) is used to describe this type of treatment.
The muscle requiring NFSE is tested to determine the amount of weight against which the muscle can perform five repetitions without causing muscle fatigue. The patient is initially taught how to identify fatigue while the therapist looks for other physical evidence of muscle fatigue. These signs of fatigue include a decrease in the quality of movement, wavering or quivering of the muscle being exercised, the use of synergistic muscles or gross body movements to help with the muscle contraction or facial grimacing of the patient while exercising.
Exercise begins with five repetitions against 50% of the amount of weight which was identified by testing. The number of repetitions is gradually increased up to 30, always making sure that fatigue is avoided. If the patient experiences fatigue, the progression of exercise intensity is stopped.
When 30 repetitions are achieved, the resistance weight is increased to 75% of the test weight and exercise is achieved without fatigue, then the protocol is begun again using 100% test weight. When a level is reached beyond which progress of exercise is impossible due to continuous fatigue, the achieved level of weight/repetition is used as a maintenance level of exercise for the particular muscle being exercised. Thus, this method of exercise is muscle- specific, with each post-polio muscle having its own maintenance exercise level.
Treatment frequency is three times weekly. Treatment is continued during the home- program maintenance on a permanent basis for both types of muscles that are encountered. A six- year maintenance of post-treatment strength has been achieved in patients who have maintained their exercise program. This compares favourably with the natural history of PPS, which is a downhill course of weakness until muscle function is no longer possible.
There are two muscles which react differently to all others in PPS. The abductor pollicis brevis and the gastrocnemius, most frequently demonstrate no evidence of recovery after acute poliomyelitis. They do not respond to exercise because of this lack of recovery. The function of plantar flexion, usually performed by the gastrocnemius, is taken over in a less efficient manner by the deeper muscles of the calf.
In addition to exercise, orthotic management often is indicated to either help or replace the function usually expected by the weakened muscles.
Also, patients are advised to take early afternoon rest periods, particularly in the presence of the generalized fatigue that usually comes on in early afternoon. These rests are incorporated into the work schedule, when necessary.
Patients are also given advice regarding energy-saving techniques and planning of high- intensity activities so as to avoid fatigue while maintaining only a slightly altered lifestyle.
All of these methods of intervention are presently provided in a clinical setting at the University of Alberta Hospitals in Edmonton, using a multidisciplinary approach to the treatment of PPS. The clinic also encourages its patients to avail themselves of the community-based support group whose members are provided with additional literature and other information regarding their disease. Clinic staff provide frequent input into meetings of the support group as well.
In the first 30 months of operation of the post-polio clinic at the University of Alberta Hospitals, 127 patients were treated with the established diagnosis of PPS. These patients presented with a total of 733 weakened muscles, of which 384 were identified as post-polio muscles and 349 were found to be weakened as a result of incomplete recovery from polio. Two hundred sixty-seven of the post-polio muscles (70%) improved in strength by at least one MRC (1 to 5 scale) grade, while the remaining 115 maintained the same level of strength that they had before treatment began. None of these muscles became weaker.
Of the 349 muscles with weakness due to incomplete recovery, in which fatigue was not avoided during exercise, 236 muscles (68%) demonstrated improvement in strength, while the remaining 113 muscles remained unchanged. Again, none demonstrated any reduction in strength with treatment.
The muscles in both groups that began treatment with Grade 3 (antigravity) strength or better improved, while muscles starting treatment with less than Grade 3 strength remained unchanged.
These results demonstrate that exercise can be used in the treatment of muscle weakness in PPS. In addition, when differentiation is made between the two different types of muscle weakness and fatigue is avoided during exercise of post-polio muscles, the results of treatment are almost identical in both types of weakness.
A properly designed exercise program, advice regarding changes in lifestyle and methods of conserving energy when performing higher-intensity activities, and orthotic management, when necessary, are appropriate components of a multidisciplinary approach to the treatment of PPS.
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