Post-polio syndrome (PPS)
24 October 2012
- Poliomyelitis (polio) is a highly infectious viral disease that mainly affects children under five years old but can strike at any age.
- Polio may cause muscle weakening and paralysis through invasion of the nervous system. It can even kill when the muscles involved in breathing are affected.
- There is no cure for polio, but it can be prevented by immunization with effective polio vaccines which have been safely in use for over 50 years.
- In 2000, the Western Pacific Region, composed of 37 countries and areas and home to over a billion people was certified as polio-free.
- While it is difficult to know the real numbers, it is estimated that there are at least over a million polio survivors.
- Post-polio syndrome (PPS) is a condition that affects polio survivors several years after initial recovery from an acute polio infection.
- While PPS is not generally life-threatening, symptoms, such as muscle weakening, may greatly affect an individual’s ability to function independently.
Who is at risk
- Though polio is a very contagious disease, PPS is not infectious.
- Only polio survivors are at risk for developing PPS, although not everyone who contracts paralytic polio will develop PPS.
- The severity of weakness of the initial polio infection may correlate with the severity in PPS.
- The exact incidence and prevalence of PPS is unknown, although some studies have estimated that PPS may develop in 25%-40% of polio survivors.
- As some people who might have been asymptomatically infected with poliovirus as children may still get PPS, it is assumed that the full burden of PPS is not known.
- PPS is mainly characterized by renewed muscle weakness in previously paralyzed muscles which had recovered or weakness in muscles that had not been previously affected, which gradually worsens with time.
- Often, new weakness presents after a period of inactivity (ie after surgery or bed rest) or subsequent to weight gain.
- Other main symptoms include decreased muscle endurance during activities, muscle and joint pain, muscle wasting and severe fatigue.
- Less common symptoms include difficulties to breathe and/or swallow.
- While the cause of PPS is not yet known, several theories have been proposed.
- One theory is that 'surviving' motor neurons become overburdened and begin to fail with age. In initial polio attacks, motor neurons that control muscles are destroyed or damaged. Surviving motor neurons grow to compensate for dead motor neurons innervating abandoned muscle cells resulting in recovered function of muscles. After many years, these surviving motor neurons, overburdened, begin to fail resulting in new muscle weakness.
- Other theories predict that the new motor neuron loss seen in PPS is due to the normal aging process.
- It has also been suggested that overuse and underuse of muscles may add to cause weakness of muscles not previously affected by paralytic polio.
- There are no laboratory tests that can specifically diagnosis PPS.
- PPS is generally difficult to diagnose as several other neuromuscular conditions may cause similar symptoms. It is recommended that patients consult an experienced specialist for a proper diagnosis.
- Five main criteria should be considered before diagnosing PPS:
- Evidence of prior infection of polio resulting in paralysis and motor neuron loss .
- Partial or complete functional recovery after acute paralytic polio followed by an interval of 15 years or more of stable neuromuscular function.
- A slowly progressive and persistent new muscle weakness or decreased endurance.
- Symptoms must persist for at least one year.
- Exclusion of other neuromuscular, medical, and skeletal abnormalities that may also cause these symptoms. It is important to rule out all other diagnoses, as while PPS has no cure, several other neuromuscular conditions do. Often, conditions may occur concurrently with PPS, such as osteoporosis, arthritis and depression.
- There is no cure for PPS, but treatment can lessen or eliminate some of these symptoms.
- PPS often takes different forms in different individuals, thus treatment plans must be tailored to each person.
- Most people can improve muscle strength and functioning through appropriate, non-fatiguing exercise.
- When exercise plans are created, physicians must identify: specific muscle groups to be included, specific muscle groups to excluded, as well as the type, frequency, and duration of exercise.
- People who are too weak or fatigued for their normal daily activities should avoid additional exercise.
- Fatigue is best treated with lifestyle changes including regular rest periods, naps, and careful planning to pace themselves throughout the day.
- When needed, the use of mobility aids and ventilation equipment may aid daily fatigue and weakness.
- Counselling is also recommended for patients and their families to assuage any fears or memories of the initial polio infection.
- There is no prevention for PPS.
- Physicians do recommend polio survivors to be diligent in taking care of themselves. A proper sleep schedule, diet and appropriate exercise is important, as well as the avoidance of smoking and weight gain.
- Recent research is exploring the role of the immune system and inflammation in PPS.
- Preliminary studies have shown intravenous immunoglobulin to be beneficial in reducing pain and increasing quality of life, but further studies are needed.