Post-Polio Syndrome Causes, Symptoms, Diagnosis, Treatment, Prevention

Post-Polio Syndrome Causes, Symptoms, Diagnosis, Treatment, Prevention

What is post-polio syndrome?

Post-polio syndrome (PPS) is a condition that affects polio survivors anywhere from 10 to 40 years after recovery from an initial paralytic attack of the poliomyelitis virus. PPS is characterized by a further weakening of muscles that were previously affected by the polio infection. Symptoms include fatigue, slowly progressive muscle weakness and, at times, muscular atrophy. Joint pain and increasing skeletal deformities such as scoliosis are common. Some patients experience only minor symptoms, while others develop spinal muscular atrophy, and very rarely, what appears to be, but is not, a form of amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease. PPS is rarely life-threatening.

The extent to which polio survivors will suffer from PPS depends on how seriously they were affected by the original polio attack. Patients who had only minimal symptoms from the original attack and subsequently develop PPS will most likely experience only mild PPS symptoms. People originally hit hard by the polio virus, who were left with severe residual weakness, may develop a more severe case of PPS with a greater loss of muscle function, difficulty in swallowing, and more periods of fatigue.

More than 300,000 polio survivors in the United States may be at risk for PPS. Doctors are unable to establish a firm incidence rate, but they estimate that the condition affects 25 percent to 50 percent of these survivors, or possibly more depending on how the disorder is defined.

What causes Post-Polio Syndrome?

Post-Polio Syndrome is caused by the death of individual nerve terminals in the motor units that remain after the initial attack of polio. This deterioration of individual nerve terminals might be an outcome of the recovery process from the acute polio attack. During this recovery process, in an effort to compensate for the loss of nerve cells (neurons), surviving motor neurons sprout new endings to restore function to muscles. This results in large motor units that may add stress to the neuronal cell body. As a result of this rejuvenation, the individual may have normal-functioning muscles for some time. But after a number of years, the motor neurons with excessive sprouting may not be able to maintain the metabolic demands of all their new sprouts, and a slow deterioration of the individual terminals may result.

Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals are destroyed and permanent weakness occurs. This hypothesis is consistent with PPS's slow, stepwise, unpredictable course. Through years of studies, scientists at the National Institute of Neurological Disorders and Stroke have shown that PPS is a very slowly progressing condition marked by long periods of stability.

Post-polio Syndrome Risks

These factors increase your chance of developing PPS. Tell your doctor if you have any of these risk factors:

  • Previous polio attack-the only absolute risk factor
  • Severity of original polio attack
  • Age at onset (worse for those who get polio later in life)

What are the symptoms of post-polio syndrome?

Symptoms include slowly progressive muscle weakness, unaccustomed fatigue (both generalized and muscular), and, at times, muscle atrophy. Pain from joint degeneration and increasing skeletal deformities such as scoliosis are common. Some patients experience only minor symptoms. While less common, others may develop visible muscle atrophy, or wasting.

Post-polio syndrome is rarely life-threatening. However, untreated respiratory muscle weakness can result in underventilation, and weakness in swallowing muscles can result in aspiration pneumonia.

The severity of residual weakness and disability after acute poliomyelitis tends to predict the development of post-polio syndrome. Patients who had minimal symptoms from the original illness will most likely experience only mild post-polio syndrome symptoms. People originally hit hard by the poliovirus and who attained a greater recovery may develop a more severe case of post-polio syndrome with a greater loss of muscle function and more severe fatigue. It should be noted that many polio survivors were too young to remember the severity of their original illness and that accurate memory fades over time.

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 post-polio syndrome. Researchers are unable to establish a firm prevalence rate, but they estimate that the condition affects 25 percent 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.

Patients diagnosed with post-polio syndrome sometimes are concerned that they are having polio again and are contagious to others. Studies have shown that this does not happen.

How is Post-Polio Syndrome diagnosed?

Doctors arrive at a diagnosis of PPS by observing the patient and asking about symptoms, and by excluding other disorders. PPS may be difficult to diagnose in some because it is hard to determine what component of a neuromuscular deficit is old and what is new. Health professionals say that the only way to be sure a person has PPS is through a neurological examination aided by other laboratory studies that exclude all other possible diagnoses. Patients must visit the doctor periodically to establish that their muscle weakness is progressive.

Objective assessment of muscle strength in PPS patients may not be easy. A change in muscle strength is determined in specific muscle groups, or limbs, using various muscle scales, such as the Medical Research Council (MRC) scale or scales that quantify muscle force. Doctors use magnetic resonance imaging (MRI), neuroimaging, and electrophysiological studies, muscle biopsies, or spinal fluid analysis as tools to investigate the course of decline in muscle strength and exclude other conditions.

Once PPS is diagnosed, some patients worry that they have polio again, or even ALS. In fact, they have neither of these disorders. In general, PPS is not life-threatening. The only exception is in patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment. Studies have proven that, compared to control populations, PPS patients lack any elevation of antibodies against the polio virus, and since PPS affects only certain muscle groups, it is not considered a recurrence of the original polio. Further, there is no evidence that the polio virus can cause a persistent infection in humans. Other studies have demonstrated that ALS, which progressively weakens muscles, does not occur more frequently in PPS patients, and PPS is not a form of ALS.

How is post-polio syndrome treated?

There are currently no effective pharmaceutical or specific treatments for the syndrome itself. However, a number of controlled studies have demonstrated that nonfatiguing exercises can improve muscle strength.

Researchers at the National Institutes of Health (NIH) have tried treating post-polio syndrome patients with alpha-2 recombinant interferon, but the treatment proved ineffective. Another study in which post-polio syndrome patients received high doses of prednisone demonstrated a mild improvement in their condition, but the results were not statistically significant. This, in addition to the drug's side effects, led researchers to recommend that prednisone not be used to treat post-polio syndrome.

In an effort to reduce fatigue, increase strength, and improve quality of life in post-polio syndrome patients, scientists conducted two controlled studies using low doses of the drug pyridostigmine (Mestinon). These studies showed that pyridostigmine is not helpful for post-polio syndrome patients.

In another controlled study scientists concluded that the drug amantadine (Symmetrel) is not helpful in reducing fatigue. And other researchers recently evaluated the effectiveness of modafinil (Provigil) on reducing fatigue and found no benefit.

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

The future of post-polio syndrome treatment may center on nerve growth factors. Since post-polio syndrome may result from the degeneration of nerve sprouts, growth factors can target these and help to regenerate new ones. Unfortunately, one small study that NINDS scientists participated in 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.

Although there is no cure, there are recommended management strategies. Seek medical advice from a physician experienced in treating neuromuscular disorders. Do not attribute all signs and symptoms to prior polio. Use judicious exercise, preferably under the supervision of an experienced professional. Use recommended mobility aids, ventilatory equipment, and revised activities of daily living. Avoid activities that cause pain or fatigue that lasts more than 10 minutes. Pace daily activities to avoid rapid muscle tiring and total body exhaustion.

Learning about post-polio syndrome is important for polio survivors and their families. Management of post-polio syndrome 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, because experiencing new symptoms and using assistive devices may bring back distressing memories of the original illness.

What is the role of exercise in the treatment of Post-Polio Syndrome?

There has been much debate about whether to encourage or discourage exercise for polio survivors or individuals who already have PPS. Some doctors believe that too much exercise can worsen the patient's condition, and that rest will preserve energy. These doctors think patients will wear out their muscles by overusing them in exercise activities. However, others consider this notion unfounded and not scientifically documented.

Researchers at the NIH recently conducted a study of exercise in PPS, not only to determine if exercise is helpful, harmful, or ineffective, but also to define the most effective type -- isotonic, isometric, isokinetic, or repetitive. Their study showed that exercise is safe and effective, and other investigators have had similar findings. A commonsense approach, in which patients use individual tolerance as their limit, is currently recommended. Tolerance is the level at which one starts having discomfort or fatigue.

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. 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 should be reduced or discontinued if additional weakness, excessive fatigue, or unduly prolonged recovery time is noted by either the individual with post-polio syndrome or the professional monitoring the exercise.

Can Post-Polio Syndrome be prevented?

People who are polio survivors often ask if there is a way to prevent PPS. Presently, no prevention has been found. But doctors recommend that polio survivors follow standard healthy lifestyle practices: consuming a well-balanced diet, exercising in moderation, and visiting a doctor regularly.

Living with Post-Polio Syndrome

Since some medical professionals do not recognize the symptoms of Post-Polio Syndrome, it is very important that a general medical evaluation be done to exclude other conditions which may mimic post-polio syndrome.

Further diagnosis and treatment by a specialist may then be necessary. Specialists dealing with post-polio syndrome include neurologists, pulmonogists, physiatrists and orthopedists.