For years, polio was one of the most feared diseases in America, responsible for crippling, paralysis and death. In 1952, according to the Centers for Disease Control and Prevention, it reached its peak in the United States with more than 21,000 paralytic cases. Shortly after that peak, vaccines were developed that greatly reduced its spread. Today, few people in developed countries get polio, thanks to immunization efforts with polio vaccine.
But some people who had polio at a young age may experience certain late effects of the disease many years later, known as a condition called post-polio syndrome (PPS). The cause of post-polio syndrome is unknown, but research is beginning to yield a better understanding of this complex condition.
According to the National Institute of Neurological Disorders and Stroke (NINDS), post-polio syndrome affects about 25 percent to 50 percent of polio survivors, perhaps even more depending on how post-polio syndrome is defined.
Treatment focuses on managing the signs and symptoms associated with post-polio syndrome and improving quality of life.
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)
Nerve cells communicate with adjacent nerve cells at contact points called synapses. Electrical impulses run along extended chains of these neurons until they reach their desired destination, as when your brain sends a message to the muscles of your legs and feet to step forward.
How polio affects nerve cells
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.
Normally, everyone loses some neurons through the aging process. But people who've had polio may have lost so many due to the infection that they end up with fewer total neurons than people who've never had polio. This may lead to the progressive weakness characteristic of post-polio syndrome. On the other hand, little evidence suggests that people who've recovered from polio lose remaining healthy neurons at a faster rate than normal.
Some scientists theorize 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. But the evidence surrounding this theory is limited, compared with the studies supporting the more generally accepted motor neuron degeneration theory.
It's possible that some of the signs and symptoms of post-polio syndrome, especially joint pain, may be due to chronic overuse of muscles that apparently were undamaged by the initial phase of polio. For example, if your left leg was disabled by polio, it may be that your right leg develops complications later in life because its muscles and joints have had to overcompensate for the disabled leg.
Risk Factor :
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. Paradoxically, 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.
When to seek medical advice :
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.
Post-polio syndrome refers to a cluster of disabling signs and symptoms that appear decades — between 10 and 40 years — after the initial illness. Common signs and symptoms include :
- New muscle weakness in limbs that were originally affected or in limbs that didn't seem to have been affected at the time of the initial illness
- General fatigue and exhaustion with minimal activity
- Muscle and joint pain
- 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.
To arrive at a diagnosis of post-polio syndrome, doctors look for three indicators :
- Previous diagnosis of polio. This may require finding old medical records or getting information from older family members, because acute polio primarily occurs during childhood. The late effects of polio usually occur in people who were age 10 or older during the initial attack of polio and whose symptoms were severe.
- Long interval after recovery. People who recover from the initial attack of polio often live for many years without further signs or symptoms. The onset of late effects varies widely, but typically begins 10 to 40 years after the initial diagnosis.
- Gradual onset. Weakness tends to be imperceptible until it interferes with daily activities. You may awaken refreshed, but feel exhausted by the early afternoon, tiring after activities that were once easy.
In addition, because the signs and symptoms of post-polio syndrome are similar to those commonly associated with other disorders, your doctor will attempt to exclude other possible causes, such as arthritis, fibromyalgia, chronic fatigue syndrome and scoliosis.
Some people with post-polio syndrome worry that they may be getting amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease. But the late effects of polio are not a form of ALS.
Some of the tests your doctor may use to rule out alternative diagnoses include :
- Electromyography (EMG) and nerve conduction studies. Electromyography measures the tiny electrical discharges produced in muscles. A thin-needle electrode is inserted into the muscles your doctor wants to study. An instrument records the electrical activity in your muscle at rest and as you contract the muscle. In a variation of EMG called nerve conduction studies (NCS), two electrodes are taped to your skin above a nerve to be studied. A small shock is passed through the nerve to measure the speed of nerve signals. These tests help identify and exclude conditions such as neuropathy, an abnormal condition of your nerves, and myopathy, a muscle tissue disorder.
- Imaging. You may undergo tests, such as magnetic resonance imaging (MRI) or computerized tomography (CT), to produce images of your brain and spinal cord. These tests can help exclude spinal disorders, such as spondylosis, a degenerative spine condition, or spinal stenosis, a narrowing of your spinal column that puts pressure on your nerves.
- Blood tests. People with post-polio syndrome usually have normal blood samples. Abnormal blood test results may indicate another underlying problem that's causing your symptoms.
Post-polio syndrome is rarely life-threatening, but severe muscle weakness can lead to complications :
- Falls. Weakness in your leg muscles makes it easier for you to lose your balance and fall. A fall may result in a broken bone, such as a hip fracture, leading to other complications.
- Malnutrition, dehydration, pneumonia. People who've had bulbar polio, which affects nerves leading to muscles involved in chewing and swallowing, often have difficulty with these activities as well as other signs of post-polio syndrome. Chewing and swallowing problems can lead to inadequate nutrition and dehydration, as well as aspiration pneumonia, which is caused by inhaling (aspirating) food particles into your lungs.
- Acute respiratory failure. Weakness in your diaphragm and chest muscles makes it harder to take deep breaths and cough, which can ultimately lead to accumulation of fluid and mucus in your lungs. Obesity, curvature of the spine, anesthesia, prolonged immobility and certain medications can further decrease breathing ability, possibly leading to acute respiratory failure. This is characterized by a sharp drop in blood-oxygen levels and may require you to undergo ventilation therapy (positive pressure ventilation).
If you're to have surgery, even dental surgery, and require general anesthesia, let your doctor or dentist know that you have post-polio syndrome. Even people with post-polio syndrome who seem healthy may have respiratory difficulties.
- Osteoporosis. Prolonged inactivity and immobility are often associated with loss of bone density and osteoporosis, in men as well as women. If you have post-polio syndrome, you may wish to be screened for osteoporosis.
Because the signs and symptoms often vary, there's no one specific treatment for post-polio syndrome. The goal of treatment is to manage your symptoms and help make you as comfortable and independent as possible.
- Energy conservation. This is probably the most important aspect of managing post-polio syndrome. It involves pacing your physical activity and combining it with frequent rest periods to reduce fatigue. Assistive devices, such as a cane, walker, wheelchair or motor scooter, also can help you conserve energy. A therapist can even show you ways to breathe that help conserve energy.
- Physical therapy. Your doctor or therapist may prescribe exercises for you that strengthen your muscles without inducing muscle fatigue. These usually include less strenuous activities, such as swimming or water aerobics, that you perform every other day at a relaxed pace. Exercising to maintain fitness is important, but be cautious in your exercise routine and daily activities. Avoid overusing your muscles and joints and attempting to exercise beyond the point of pain or fatigue. Otherwise, you may need several days' rest to regain your strength.
- Occupational therapy. A physical or occupational therapist can help you modify your home environment so that it's safe and convenient for you. This may include installation of grab bars in the shower or a raised toilet seat. Your therapist may also help you rearrange furniture or rethink certain household or work-related tasks, decreasing the number of steps you must take and increasing your efficiency.
- Speech therapy. A speech therapist can show you ways to compensate for swallowing difficulties.
- Sleep apnea treatment. Treatment for sleep apnea, which is common among people with post-polio syndrome, may involve changing your sleeping patterns, such as avoiding sleeping on your back, or using a device that helps open up a blocked airway.
- Medications. Medications, including aspirin and other nonsteroidal anti-inflammatory drugs, may ease muscle and joint pain. Certain drugs — pyridostigmine (Mestinon), amantadine (Symmetrel), selegiline (Eldepryl) and bromocriptine (Parlodel) — have been studied as a treatment for the fatigue of post-polio syndrome, but no clear benefit has yet been shown. Other medications for fatigue may help, such as modafinil (Provigil). Studies of insulin-like growth factor-I (IGF-I), a medication designed to improve muscle strength, showed that although it doesn't change strength or susceptibility to fatigue, it does improve recovery after exercise.