Post-polio syndrome (PPS) can begin to affect victims of polio up to 40 years after that first infection. This may eventually happen in up to 80 percent of all victims of polio.
The explanation for the existence of PPS is uncertain, though there are a few theories.
The original poliovirus may have been dormant for many years and been reactivated, perhaps due to an accident, illness, trauma or excessive stress.
What would cause reactivation is unknown. But it is known that polio antibodies have been discovered in PPS patients' spinal fluid.
Here's another theory. After nerve cells (neurons) were damaged or killed by the original poliovirus, healthy neurons took their places.
A neuron plus the muscle fibers it moves are called a motor unit. After the original poliovirus killed some neurons, healthy neurons generated new terminals for muscle fibers whose neurons died.
The motor units are bigger than before, since the healthy neurons are now tending more muscle fibers than they were meant to. They may simply wear out before their time. Symptoms experienced earlier by victims of polio return.
Symptoms may be repeats of the originals suffered by the victims of polio, though this isn't always the case. It's possible for PPS to damage muscles that were not previously affected by polio.
Breathing difficulties cause inadequate oxygen intake, and ventilation assistance may be necessary. Trouble swallowing because of weakness can lead to aspiration pneumonia.
Skeletal abnormalities like scoliosis may occur. Exhaustion, debilitating fatigue, pain in the lower back, joint and muscle pain, muscle wasting (atrophy), progressive muscle weakness, make daily life extremely draining.
Sleep problems and temperature hypersensitivity add to the disordered experience of living with post-polio syndrome. The severity of symptoms from PPS will largely correspond to the severity suffered from polio.
Exercise is tricky. Some exercise may help but the wrong kind or too much of it can cause setbacks. It's important to respond immediately to signs of fatigue, pain or spasms. Otherwise, symptoms can be aggravated for extended periods.