What is believed to cause the symptoms of Post-Polio Syndrome?

• A. Overuse or over-compensation of polio-damaged motor neurons by healthy ones.
• B. Reinfection with poliovirus
• C. Vitamin deficiency
• D. Bacterial infection

Answer: (A)

Post-Polio Syndrome is thought to arise from the long-term effects on motor neurons that were damaged by polio. After the initial infection, surviving motor neurons sprout new branches to reinnervate muscle fibers, creating enlarged motor units to compensate for the lost fibers. Over many years, these overworked, reinnervated neurons can gradually deteriorate or fatigue, leading to new weakness, fatigue, and muscle wasting long after the initial illness. This neuronal wear-and-tear explanation fits the late onset of symptoms and the pattern of weakness seen in PPS.

The other ideas don’t fit as the cause. Reinfestation with poliovirus isn’t how polio or PPS works once immunity is established; vitamin deficiencies or bacterial infections aren’t established drivers of PPS.