Which statement best describes the etiology of post-polio syndrome?

• A. Overstressed anterior horn cells due to collateral sprouting leading to progressive decline
• B. Autoimmune demyelination
• C. Purely genetic
• D. Degeneration of the neuromuscular junction due to aging

Answer: (A)

Post-polio syndrome arises from long-term stress on motor neurons that survived the initial poliovirus attack. When polio destroys many anterior horn cells, the remaining neurons sprout collateral branches to reinnervate the denervated muscle fibers, creating enlarged motor units. These oversized, overworked units can keep function for years, but their neurons become metabolically strained and eventually degenerate. Over time this leads to new weakness, fatigue, and muscle loss that appear long after the original illness. This pattern fits PPS best because it centers on motor neuron overuse and gradual decline of those overstressed units, rather than autoimmune demyelination, purely genetic causes, or aging-related changes at the neuromuscular junction.