What is the cause of post-polio syndrome (PPS)?

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The cause of post-polio syndrome (PPS) is unknown. However, the new weakness of PPS appears to be related to the degeneration of individual nerve terminals in motor units that remain after the initial illness. A motor unit is a nerve cell (or neuron). Poliovirus attacks specific neurons in the brain stem and the anterior horn cells of the spinal cord. In an effort to compensate for the loss of these neurons, ones that survive sprout new nerve terminals to orphaned muscle fibers. The result is some recovery of movement and enlarged motor units.

Years of high use of these enlarged motor units adds stress to the neuronal cell body, which then may not be able to maintain the metabolic demands of all the new sprouts, resulting in the slow deterioration of motor units. Restoration of nerve function may occur in some fibers the second time, but eventually, nerve terminals malfunction and permanent weakness occurs. This hypothesis is consistent with PPS's slow, stepwise, unpredictable course.

Through years of studies, scientists at the National Institute of Neurological Disorders and Stroke and at other institutions have shown that the weakness of PPS is a very slowly progressing condition marked by periods of stability followed by new declines in the ability to carry out usual daily activities.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

Continue Learning about Viral Infections

Viral Infections

Viral Infections

Viral infections like herpes simplex, respiratory syncytial virus (RSV), chicken pox and rotavirus are infections caused by a virus instead of a bacterium. Viral infections do not respond to antibiotics, but some specific viruses ...

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.