Causes

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 � 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)

A polio infection often damages or destroys many of these motor neurons. To compensate for the resulting neuron shortage, the remaining neurons sprout new fibers, and the surviving motor units enlarge.

This promotes recovery of the use of your muscles, but it also pushes 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, of the neuron itself.