Post-polio syndrome overview

Post-polio syndrome (PPS) is a condition that affects survivors of poliomyelitis, a viral infection of the nervous system, after recovery from an initial paralytic attack of the virus.

The precise mechanism that causes post-polio syndrome is unknown.

PPS has been confused with amyotrophic lateral sclerosis (ALS), which progressively weakens muscles. PPS patients do not have an elevated risk of ALS.

PPS shares many features in common with myalgic encephalomyelitis, a form of chronic fatigue syndrome that is apparently caused by viral infections, but unlike those disorders it tends to be progressive, and can cause tangible loss of muscle strength.

In general, PPS is not life-threatening. The major exception are patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment.There have been no sufficient longitudinal studies on the prognosis of post-polio syndrome; however, speculations have been made by several physicians based on experience. Fatigue and mobility usually return to normal over a long period of time. The prognosis also differs depending upon different causes and factors affecting the individual. An overall mortality rate of 25% exists due to possible respiratory paralysis of persons with post-polio syndrome; otherwise, post-polio syndrome is usually non-lethal.^[1]

Typically the symptoms appear 20-40 years after the original infection, at an age of 35 to 60. Symptoms include new or increased muscular weakness, pain in the muscles, and fatigue.^[2]

Diagnosis of post-polio syndrome can be difficult, since the symptoms are hard to separate from the original symptoms of polio and from the normal infirmities of aging. There is no laboratory test for post-polio syndrome, nor is there any other specific diagnostic, and diagnosis is usually a “diagnosis of exclusion” whereby other possible causes of the symptoms are eliminated.^[3]

PPS may be difficult to diagnose in some because it is hard to determine what component of a neuromuscular deficit is old and what is new: Neurological examination aided by other laboratory studies can help to exclude all other possible diagnoses. Objective assessment of muscle strength in PPS patients may not be easy. Changes in muscle strength are determined in specific muscle groups sing various muscle scales which quantify strength, such as the Medical Research Council (MRC) scale.

Muscle biopsies and spinal fluid analysis may also be used in establishing a PPS diagnosis.

Magnetic resonance imaging (MRI) and neuroimaging may also be used in establishing a PPS diagnosis.

Electrophysiological studies may also be used in establishing a PPS diagnosis.

Treatment generally is limited to supportive measures, primarily leg braces and energy-saving devices such as powered wheelchairs, plus pain relievers, sleep aids, etc.

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