Polio and Post-Polio Syndrome
Also called: Infantile paralysis, Poliomyelitis, PPS
Polio is an infectious disease caused by a virus. It attacks your nervous system. In rare cases, polio infection can cause paralysis. Polio vaccination will protect most people for life. The United States and most other countries eradicated polio decades ago, except for rare cases.
The disease most commonly affects young children. Poliovirus spreads in human waste. People usually get it from contaminated food or water. Symptoms include fever, tiredness, vomiting, neck stiffness, and leg and arm pain. Most infected people never have symptoms. No treatment will reverse polio paralysis. Moist heat, physical therapy and medicines might ease symptoms.
Some people who've had polio develop post-polio syndrome (PPS) years later. Symptoms include tiredness, new muscle weakness and muscle and joint pain. There is no way to prevent or cure PPS.
World Health Organization
Post-polio syndrome (PPS) is a condition that some people who had polio at a young age may experience years later.
Polio was once one of the most feared diseases in America, responsible for paralysis and death. Shortly after polio reached its peak in the early 1950s, the inactivated polio vaccine was introduced and greatly reduced polio's spread. Today, few people in developed countries get paralytic polio, thanks to the polio vaccine.
But some people who had polio at a young age may experience certain late effects of the disease many years later — post-polio syndrome. The exact cause of post-polio syndrome is unknown.
Treatment focuses on managing the signs and symptoms of post-polio syndrome and improving your quality of life.
Post-polio syndrome refers to a cluster of disabling signs and symptoms that appear decades — an average of 30 to 40 years — after the initial illness. Common signs and symptoms include:
* Progressive muscle and joint weakness and pain
* General fatigue and exhaustion with minimal activity
* Muscle atrophy
* Breathing or swallowing problems
* Sleep-related breathing disorders, such as sleep apnea
* Decreased tolerance of cold temperatures
In most people, post-polio syndrome tends to progress slowly, with new signs and symptoms followed by periods of stability.
When to see a doctor
If you're experiencing weakness or fatigue that seems to be slowly getting worse, see your doctor. It's important to rule out other causes of your signs and symptoms that may require different therapy from what's currently advised for post-polio syndrome.
Nobody knows exactly what causes the signs and symptoms of post-polio syndrome to appear so many years after the first episode of polio. Currently, the most accepted theory regarding the cause of post-polio syndrome rests on the idea of degenerating nerve cells.
When poliovirus infects your body, it affects nerve cells called motor neurons — particularly those in your spinal cord — that carry messages (electrical impulses) between your brain and your muscles.
Each neuron consists of three basic components:
* A cell body
* A major branching fiber (axon)
* Numerous smaller branching fibers (dendrites)
A polio infection often leaves many of these motor neurons destroyed or damaged. To compensate for the resulting neuron shortage, the remaining neurons sprout new fibers, and the surviving motor units become enlarged. This promotes recovery of the use of your muscles, but it also places added stress on the nerve cell body to nourish the additional fibers. Over the years, this stress may be more than the neuron can handle, leading to the gradual deterioration of the sprouted fibers and, eventually, the neuron itself.
Another theory is that the initial illness may have created an autoimmune reaction, causing the body's immune system to attack normal cells as if they were foreign substances. Some experts believe that the poliovirus may persist in the body and reactivate years later.
Factors that may increase your risk of developing post-polio syndrome include:
* Severity of initial polio infection. The more severe the initial infection, the more likely that you'll have signs and symptoms of post-polio syndrome.
* Age at onset of initial illness. If you acquired polio as an adolescent or adult, rather than as a young child, your chances of developing post-polio syndrome increase.
* Recovery. The greater your recovery after acute polio, the more likely it seems that post-polio syndrome will develop. This may be because greater recovery places additional stress on motor neurons.
* Physical activity. If you often perform physical activity to the point of exhaustion or fatigue, this may overwork already stressed-out motor neurons and increase your risk of post-polio syndrome.
The symptoms of pain, weakness, and fatigue can result from the overuse and misuse 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. 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 additional weakness, excessive fatigue, or unduly prolonged recovery time is noted by either the individual with PPS or the professional monitoring the exercise.
Can PPS be prevented?
Polio survivors often ask if there is a way to prevent 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, the use of assistive devices, and taking certain anti-inflammatory medications may help some of the symptoms of PPS.
What research is being conducted?
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.
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 if this is due to an immunological response.
Other investigators have discovered that fragments of the poliovirus, or mutated versions of it, are in the spinal fluid of some survivors. The significance of this finding is not known and more research is being done.