Post-Polio Syndrome Fact Sheet

Polio, or poliomyelitis, is an infectious viral disease that can strike at any age and affects a person's nervous system.  In the late 1940s to the early 1950s in the United States alone, polio crippled around 35,000 people each year, making it one of the most feared diseases of the twentieth century.

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.  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 (curvature of the spine) are common and may precede the weakness and muscle atrophy. Some individuals experience only minor symptoms while others develop visible muscle weakness and atrophy.

PPS is rarely life-threatening, but the symptoms can interfere significantly with the individual's ability to function independently.  Respiratory muscle weakness, for instance, can result in trouble with proper breathing, affecting daytime functions and sleep.  Weakness in swallowing muscles can result in aspiration of food and liquids into the lungs and lead to pneumonia.

The severity of weakness and disability after recovery from poliomyelitis tends to predict who might be at higher risk of developing PPS. Individuals who had minimal symptoms from the original illness are more likely to experience only mild PPS symptoms. People originally hit hard by the poliovirus attack and who attained a greater recovery may experience a more severe case of PPS, with greater loss of muscle function and more severe fatigue.  

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. Researchers estimate that the condition affects 25 to 50 percent of polio survivors.

While polio is a contagious disease, PPS is not transmissible, but one must be a polio survivor to contract 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 brain stem and 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 brain stem 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 and connect with the orphaned muscle fibers.  These new connections result in recovery of movement and gradual gain in power in the affected limbs.

Years of high use of these recovered but overly extended motor units adds stress to the motor neurons, which after years are no longer able to maintain the increased work demands.  This results in the slow deterioration of the neurons, resulting in loss of muscle strength. Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals malfunction and permanent weakness occurs. This hypothesis explains why PPS occurs after a delay and has a slow and progressive course.

Through years of studies, scientists at the National Institute of Neurological Disorders and Stroke and at other institutions have shown that the weakness of PPS progresses very slowly.  It is marked by periods of relative stability interspersed with periods of decline.

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. 

Physicians typically use the following criteria when diagnosing PPS:

PPS may be difficult to diagnose in some people because other medical conditions can complicate the evaluation. Depression, for example, is associated with fatigue and can be misinterpreted as PPS. A number of conditions may cause problems in persons wit polio whether or not due to additional loss of motor neuron function. For example, shoulder osteoarthritis from walking with crutches, a chronic rotator cuff tear leading to pain and disuse weakness, or progressive scoliosis causing breathing insufficiency can occur years after polio bot are not indications of the PPS.

Polio survivors with new symptoms resembling PPS should consider seeking treatment from a physician trained in neuromuscular disorders.  It is important to clearly establish the origin and potential causes for declining strength and to assess progression of weakness not explained by other health problems.

Magnetic resonance imaging (MRI) and computed tomography (CT), of the spinal cord, electrophysiological studies, and other tests are frequently used to investigate the course of decline in muscle strength, and to exclude other diseases that could be causing or contributing to the new progressive symptoms.  A muscle biopsy or a spinal fluid analysis can be used to exclude other, possibly treatable, conditions that mimic PPS.  However, no test can diagnose PPS or identify which polio survivors are at greatest risk.

Polio survivors may acquire other illnesses and should always have regular check-ups and preventive diagnostic tests.

There are currently no effective pharmaceutical treatments that can stop deterioration or reverse the deficits caused by for the syndrome itself. However, a number of controlled studies have demonstrated that nonfatiguing exercises may improve muscle strength and reduce tiredness.    Most of the clinical trials in PPS have focused on finding safe therapies that could reduce symptoms and improve quality of life.

Researchers at the National Institutes of Health (NIH) have tried treating PPS patients with high doses of steroids (prednisone) and demonstrated a mild improvement in their condition, but the results were not statistically significant.  Also, the side effects from the treatment outweighed benefits, leading researchers to conclude that prednisone not be used to treat PPS.

Preliminary studies indicate that intravenous immunoglobin may reduce pain, increase quality of life, and improve strength modestly. Research into its use is ongoing. 

The future of PPS treatment may center on nerve growth factors. Since PPS may result from the degeneration of nerve sprouts, growth factors that target these terminals might preserve their health or help to regenerate new ones. Unfortunately, one small study showed that insulin-like growth factor (IGF-1), which can enhance the ability of motor neurons to sprout new branches and maintain existing branches, was not helpful.

Several compounds have been tested but shown to be ineffective in treating PPS.  Two controlled studies using low doses of the drug pyridostigime (Mestinon, used to treat muscle weakness in patients with myasthenia gravis) found it was not helpful in reducing fatigue or increasing strength in individuals with PPS.  Controlled studies of the drugs amantadine (a treatment for muscle weakness and fatigue) and modafinil (Provigil, which promotes wakefulness) also found no benefit on reducing fatigue in persons with PPS.  A small trial to treat fatigue using lamotrigine (an anaticonvulsand drug) showed modest effect but this study was limited and larger, more controlled studies with the drug were not conducted to validate the findings. 

Although there is no cure, there are recommended management strategies. Patients should consider seeking medical advice from a physician experienced in treating neuromuscular disorders. Patients should also consider judicious use of exercise, preferably under the supervision of an experienced professional. Physicians often advise patients on the use of mobility aids, ventilation equipment, revising activities of daily living to avoid rapid muscle tiring and exhaustion, and avoiding activities that cause pain or fatigue lasting more than 10 minutes. Most importantly, patients  should avoid the temptation to attribute all signs and symptoms to prior polio and thereby missing out on important treatments for concurrent conditions.

Learning about PPS is important for polio survivors and their families. Management of PPS can involve lifestyle changes. Support groups that encourage self-help, group participation, and positive action can be helpful. For some, individual or family counseling may be needed to adjust to the late effects of poliomyelitis.  Experiencing new symptoms of weakness and using assistive devices may bring back distressing memories of the original illness.

The symptoms of pain, weakness, and fatigue can result from the overuse of muscles and joints. These same symptoms can also result from disuse of muscles and joints. This fact has caused a misunderstanding about whether to encourage or discourage exercise for polio survivors or individuals who already have 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, and
• the type of exercise, together with frequency and duration.

Exercise should be reduced or discontinued if it is associated with additional weakness, excessive fatigue, or unduly prolonged recovery time that 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.

Polio survivors often ask if there is a way to prevent the development of PPS. Presently, no intervention has been found to stop the deterioration of surviving neurons. But physicians recommend that polio survivors get the proper amount of sleep, maintain a well-balanced diet, avoid unhealthy habits such as smoking and overeating, and follow an exercise program as discussed above. Proper lifestyle changes, especially with regard to eating style and body weight control, the use of assistive devices, and taking certain anti-inflammatory medications may help some of the symptoms of PPS.

Scientists are working on a variety of investigations that may one day help individuals with PPS. Some basic researchers are studying the behavior of motor neurons many years after a polio attack. Others are looking at the mechanisms of fatigue and are trying to discover the role played by the brain, spinal cord, peripheral nerves, the neuromuscular junction (the site where a nerve cell meets the muscle cell it helps activate), and the muscles. Another study is examining whether mental impairment is present in individuals with PPS and, if so, how it interferes with self-functioning.

Determining if there is an immunological link in PPS is also an area of intense interest. Researchers who discovered inflammation around motor neurons or muscles are trying to find out what causes this immunological response.