What is post-polio syndrome?
Post-polio syndrome (PPS) is a condition that affects polio survivors years after recovery from an initial acute attack of the poliomyelitis virus. Most often, polio survivors start to experience gradual new weakening in muscles that were previously affected by the polio infection and also in muscles that seemingly were unaffected by the virus.
What are the symptoms of PPS?
The most common symptoms include slowly progressive muscle weakness, fatigue (both generalized and muscular) and a gradual decrease in the size of muscles (muscle atrophy). Pain from joint degeneration and increasing skeletal deformities such as scoliosis are common and may precede the weakness and muscle atrophy. Some individuals experience only minor symptoms while others develop visible muscle weakness and atrophy.
What causes PPS?
The cause of PPS is unknown but experts have offered hypotheses to explain the phenomenon. The new weakness of PPS appears to be related to the degeneration of individual nerve terminals in the motor units that remain in the spinal cord after the initial illness. A motor unit is formed by a nerve cell (or motor neuron) and the muscle fibers it activates. The poliovirus attacks specific neurons in the brainstem and the anterior areas of the spinal cord. In an effort to compensate for the loss of these motor neurons, ones that survives the virus attack sprout new nerve-end terminals, connecting with the orphaned muscle fibers–which may result in recovery of movement and gradual gain in power in the affected limbs.
How is PPS diagnosed?
The diagnosis of PPS relies nearly entirely on clinical information. There are no laboratory tests specific for this condition and symptoms may vary greatly among individuals. Physicians arrive at a diagnosis of PPS by completing a comprehensive medical history and physical examination and by excluding other disorders that could explain the symptoms. Researchers and physicians typically use the following criteria to establish a diagnosis:
- Prior paralytic poliomyelitis with evidence of motor neuron loss, as confirmed by history of the acute paralytic illness, signs of residual weakness and atrophy of muscles on neuromuscular examination, and signs of nerve damage on electromyography (EMG). Rarely, persons have subclinical paralytic polio, described as a loss of motor neurons during acute polio but with no obvious deficit. That prior polio now needs to be confirmed with an EMG. Also, a reported history of nonparalytic polio may be inaccurate
- A period of partial or complete functional recovery after acute paralytic poliomyelitis, followed by an interval (usually 15 years or more) of stable neuromuscular function.
- Gradual onset of progressive and persistent new muscle weakness or abnormal muscle fatigability (decreased endurance), with or without generalized fatigue, muscle atrophy, or muscle and joint pain. Onset may at times follow trauma, surgery, or a period of inactivity, and can appear to be sudden. Less commonly, symptoms attributed to PPS include new problems with breathing or swallowing.
- Symptoms that persist for at least a year
- Exclusion of other neuromuscular, medical, and orthopedic problems as causes of symptoms
How is PPS treated?
There are currently no effective pharmaceutical treatments that can stop deterioration or reverse the deficits caused by for the syndrome itself. Although there is no cure, there are recommended management strategies. Seek medical advice from a physician experienced in treating neuromuscular disorders.
How common is PPS?
The exact incidence and prevalence of PPS continues to be unknown. Studies have shown a wide difference regarding the prevalence of PPS within different areas of the same nation, or between different nations. According to estimates by the National Center for Health Statistics, more than 440,000 polio survivors in the United States may be at risk for PPS. Researchers estimate that the condition affects 25 to 50 percent of these survivors, or possibly as many as 60 percent, depending on how the disorder is defined and which study is quoted.
What is the role of exercise in the treatment of PPS?
Exercise is safe and effective when carefully prescribed and monitored by experienced health professionals. Exercise is more likely to benefit those muscle groups that were least affected by polio. Cardiopulmonary endurance training is usually more effective than strengthening exercises, especially when coupled with the pacing of activities to allow for frequent breaks and strategies to conserve energy. Heavy or intense resistive exercise and weight-lifting using polio-affected muscles may be counterproductive because they can further weaken rather than strengthen these muscles.
Exercise prescriptions should include:
- the specific muscle groups to be included
- the specific muscle groups to be excluded
- the type of exercise, together with frequency and duration
Exercise should be reduced or discontinued if additional weakness, excessive fatigue, or unduly prolonged recovery time is noted by either the individual with PPS or the professional monitoring the exercise. As a general safe rule, no muscle should be exercised to the point of causing ache, fatigue, or weakness.
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