Post-polio syndrome

Post-polio syndrome is a group of potentially disabling signs and symptoms that appear decades after the initial polio illness. These signs and symptoms usually appear between 30 to 40 years after having polio.

Infection from the polio virus once caused paralysis and death. However, the introduction of the inactivated polio vaccine in the 1950s greatly reduced polio's spread.

Today, very few people in developed countries are paralyzed from the polio virus, usually related to a reaction from one form of the vaccine. However, there remain many people who had polio at a young age who now later in life might develop the post-polio syndrome.

Post-polio syndrome only affects people who had polio. Common signs and symptoms of post-polio syndrome include:

• Muscle and joint weakness and pain that gets worse over time
• Feeling easily fatigued and exhausted
• Losing muscle tissue (atrophy)
• Breathing or swallowing problems
• Sleep-related breathing disorders, such as sleep apnea
• Decreased tolerance of cold temperatures

Post-polio syndrome progresses slowly in most people. They may experience new signs and symptoms followed by periods of stability.

See your doctor if you have increasing weakness or fatigue. It's important to rule out other causes of your signs and symptoms and determine whether you have post-polio syndrome.

There are several theories as to what causes post-polio syndrome, but no one knows for sure.

When poliovirus infects your body, it affects nerve cells called motor neurons that carry messages (electrical impulses) between your brain and your muscles. Poliovirus particularly affects the motor neurons in the spinal cord.

Each motor neuron consists of three basic components:

• A cell body
• A major branching fiber (axon)
• Numerous smaller branching fibers (dendrites)

A polio infection often damages or destroys many of these motor neurons. Because there are fewer motor neurons, the remaining neurons sprout new fibers and grow bigger.

This promotes recovery of the use of your muscles, but it also may stress the nerve cell body to nourish the additional fibers. Over the years, this stress may be too much. This may cause the gradual breakdown of the sprouted fibers and, eventually, of the neuron itself.

Factors that can 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 developed polio as an adolescent or adult rather than as a 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.
• Excessive physical activity. If you often exercise to the point of exhaustion or fatigue, you might overwork already stressed-out motor neurons and increase your risk of post-polio syndrome.

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. You then might break a bone, such as a hip, leading to other complications.
• Fatigue. Fatigue is very common in people with post-polio syndrome. The fatigue may be disabling, even after very little activity. It may also lead to problems with concentration and memory.
• Pain. Musculoskeletal abnormalities and muscle weakness can lead to chronic pain.

• Malnutrition, dehydration and pneumonia. People who've had bulbar polio, which affects nerves leading to muscles involved in chewing and swallowing, often have difficulty with these activities and have other signs of post-polio syndrome.

  Chewing and swallowing problems can lead to inadequate nutrition and to dehydration, as well as to aspiration pneumonia, which is caused by inhaling food particles into your lungs (aspirating).

• Chronic respiratory failure. Weakness in your diaphragm and chest muscles makes it harder to take deep breaths and cough, which can cause fluid and mucus to build up in your lungs.

  Obesity, smoking, curvature of the spine, anesthesia, prolonged immobility and certain medications can further decrease your breathing ability, possibly leading to a sharp drop in blood oxygen levels (acute respiratory failure). You might then need treatment to help you breathe (ventilation therapy).

• Osteoporosis. Prolonged inactivity and immobility are often accompanied by loss of bone density and osteoporosis in both men and women. If you have post-polio syndrome, talk to your doctor about bone density screening.
• Sleep disorders. Sleep apnea and restless legs syndrome are common in people with post-polio syndrome. These sleep disorders may worsen insomnia and fatigue if untreated.