Post-polio syndrome is defined by a collection of symptoms that generally occur at least 10 to 20 years after infection with the polio virus. The hallmark of post-polio syndrome is new muscular weakness. This may present as weakness in the arms, legs or trunk, or difficulty with swallowing, talking or breathing if the muscles that control these functions are affected. Other symptoms of post-polio syndrome include muscle pain, fatigue and cold intolerance. It is not uncommon for polio survivors to have new weakness in muscles that were previously believed to be unaffected by polio. This may be because they really weren't sure which muscles were affected many years before, or because muscles were so mildly affected at first that doctors didn't detect it on physical examination at the time of the polio virus infection.

Polio is a disease caused by an infection with the poliovirus. In a small number of cases (less than 10%), the virus will attack the cells in the spinal cord and cause paralysis. Because the initial illness was a long time ago and the details are often sketchy, establishing an old history of polio and paralysis can be challenging. For example, in some of these cases, (such as when a child is very sick with a high fever and headache) it might not be obvious if there is some paralysis, because the patient is just sick and too exhausted to move well. Another factor that adds to the confusion is that people with post-polio syndrome typically had polio many years ago. So, the history of what actually happened all those years ago is often inaccurate. For these reasons, the terms "paralytic" and "nonparalytic" polio have dropped out of favor. Today, most experts believe that there is a continuum of paralysis in a small number of cases and it isn't always clear to doctors whether the spinal cord was previously involved and to what extent.

It's not clear how many polio survivors will be affected by post-polio syndrome. A reasonable estimate is 60% of those who had significant paralysis during the initial illness. It's also not clear why some polio survivors develop post-polio syndrome. Likely it has to do with multiple factors. One suspected factor is overuse of the nerves and muscles that remained working after the initial infection. Years of overuse may accelerate the dropout of motor nerve axons and lead to new weakness.

Polio that affects the spinal cord usually destroys many 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.

Normal aging likely also contributes to new weakness. Nervous system damaged by polio years earlier goes through a natural aging process that includes the loss of some strength.

After recovering from polio, since you have a smaller number of nerve cells (think of this as not having the normal reserve of strength that someone without a history of polio might have to accomplish daily tasks like walking or lifting a gallon of milk), 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 leave you more susceptible to weakness that you might not otherwise notice.

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. However, this question remains controversial.

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 weakness, pain, 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, talking, 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 is no specific test that diagnoses post-polio syndrome. Instead, the diagnosis is made by confirming an old history of polio (based on history, physical examination and a muscle test called an electromyogram, or EMG). In addition to these, there needs to be a period of partial recovery after the initial illness and a long stable period without new symptoms (at least 10 to 20 years).

Finally, other reasons why someone may be experiencing new symptoms need to be ruled out. Your doctor will ask about your medical history, especially your history of polio. A neurological exam can identify muscle weakness and atrophy. An EMG can help to diagnose this disease. In this procedure, small needles are inserted into several areas of muscle. Of note, EMGs are often done in conjunction with another test called nerve conduction studies (NCS), which don't typically use needles but instead have surface electrodes that deliver small amounts of electricity to test the nerves. 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.

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.

Specific treatment for post-polio syndrome includes a multi-disciplinary rehabilitation approach. Physical therapy may be used to increase muscle strength and endurance and to help with improving balance and preventing falls. Occupational therapists can address upper extremity problems, especially overuse injuries, as well as recommend adaptive equipment for your home and/or office. Speech and language pathologists evaluate and treat swallowing and speech problems. Orthotists can fit you for an up-to-date brace. Neurologists and physiatrists are usually the physician specialists who care for people with post-polio syndrome. Physiatrists are doctors who specialize in Physical Medicine and Rehabilitation (PM and R) and can help to both establish the diagnosis and treat any symptoms. Both physiatrists and neurologists are often trained in performing EMG testing. For treatment, these doctors may prescribe medications to help with pain and/or fatigue or perform injections. They may recommend sleep studies and prescribe treatments that help with breathing at night. They can write specific therapy orders, brace prescriptions and help coordinate the multi-disciplinary interventions.

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 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. With a combination of multi-disciplinary rehabilitation approaches 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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