Post-polio syndrome is pain, muscle weakness and fatigue that occur 15 to 30 years after recovery from polio (paralytic poliomyelitis). Symptoms always involve one or more of the same muscle groups affected during the polio infection.

Most experts believe post-polio syndrome is caused when a nervous system damaged by polio years earlier goes through a natural aging process. Polio is an infection with the poliovirus. Polio that affects the spinal cord usually destroys about half of the motor neurons (nerve cells) that control the muscles of the body. During recovery from polio, you can't build new nerve cells. However, you can create new connections between surviving nerve cells and muscles, so you can recover your muscle strength by "re-wiring" your nerve connections. This is an effective way for your nervous system to compensate for polio, but it may be temporary.

After recovering from polio, since you have a smaller number of nerve cells, you can't afford to have nerve cells stop working. Yet, polio is not the only thing that can damage nerve cells. As years pass, nerve cells can be disabled or damaged by illness, injury, your own immune system or natural aging. Delicate connections between nerves and muscles can be lost during periods of inactivity. If you are already relying on a smaller number of nerve cells than is normal, then this loss of other nerve cells over time might allow some of your original polio symptoms to show through.

Scientists are almost certain that any living poliovirus is eliminated many years before post-polio symptoms appear. Some scientists have searched for poliovirus in patients with post-polio syndrome, but they have not found convincing evidence that virus remains.

The syndrome is more common among people who had polio during adolescence or adulthood (rather than during young childhood) and people who overcame symptoms that were initially severe.

People usually are affected during middle or late adult life after a long period of stability following polio. The new symptoms sometimes emerge after an illness or injury.

Major symptoms include muscle pain, weakness, fatigue and, in some cases, wasting (atrophy) of the muscles that were involved during the polio infection, typically the legs. Additional problems can include intolerance to heat or cold, and difficulty swallowing, breathing or sleeping. The syndrome also can cause abnormal muscle contractions, such as quivering or spasms, in small segments of a muscle. Worsening disability may cause social and psychological problems. There also can be numbness or tingling, but these sensory problems are uncommon.

Your doctor will ask about your medical history, especially your history of polio. A neurological exam can identify muscle weakness and atrophy. A test called an electromyelogram can help to diagnose this disease. In this procedure, small needles are inserted into several areas of muscle. Mild electric currents are used to stimulate muscle contraction so that their strength and function can be estimated even when nerves are not able to signal the muscles to work. When the diagnosis is uncertain, an electromyelogram can help to sort out whether weakness is caused by a muscle disease or by nerve problems.

Post-polio syndrome worsens slowly over time, then usually stops getting worse after 1 to 10 years.

In people who have a history of polio, there is no good way to prevent post-polio syndrome. Children and unvaccinated adults who are traveling to underdeveloped countries should be vaccinated against polio.

There is no specific treatment for post-polio syndrome. Physical therapy may be used to increase muscle strength and endurance. You also can modify your lifestyle; for example, by adjusting your pace of exercise to avoid rapid fatigue. Bracing, orthotics and other aids may support or substitute for affected muscles.

Complications that involve swallowing or breathing disturbances (such as sleep apnea) require specific treatments. Examples might include using different positions during meals, or an air-pressure mask and machine that can be used during sleep to support breathing. Counseling with a psychologist, occupational therapist or vocational counselor can help with psychological or occupational adjustments. Support groups offer education, support and social opportunities.

Call a health care professional if you notice changes in muscle strength, decreased endurance, muscle wasting or abnormal muscle twitching. Difficulties swallowing, breathing or sleeping also require medical attention.

Post-polio syndrome usually worsens slowly and stops progressing after 1 to 10 years. With a combination of physical therapy and lifestyle modifications, people often can return to or approach their previous level of functioning. Post-polio syndrome does not usually cause symptoms that are as severe as the original polio illness.

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