Residual weakness in polio survivors is best described as what?

• A. Irreversible motor neuron loss
• B. Reversible motor neuron loss
• C. Temporary motor fatigue
• D. Complete recovery with therapy

Answer: (A)

Poliovirus damages the motor neurons in the spinal cord, specifically the anterior horn cells, and that loss is permanent. When these neurons die, the number of motor units available to contract muscles is permanently reduced, so weakness persists long after the acute illness has resolved. Surviving neurons can sprout to reinnervate orphaned muscle fibers, which helps regain some function, but it doesn’t replace the lost neurons. That’s why residual weakness is best described as irreversible motor neuron loss. It isn’t simply temporary fatigue, and while therapy can improve function, it can’t fully restore what was lost to neuron death.