DN> From: nyeda@cnsvax.uwec.edu (David Nye)
DN> Briefly, this is a condition in which patients who have significant
DN> residual weakness from childhood polio notice progression of the
DN> weakness as they get older.  One theory is that the remaining motor
DN> neurons have to work harder and so die sooner.

If this theory were true, the muscle biopsy would show group atrophy
(evidence of acute loss of enlarged motor units); it doesn't.
Instead, the biopsy shows scattered, angulated, atrophic fibers.
This is more consistent with load-shedding by chronically overworked
motor neurons - the neurons survive, at the expense of increasingly
denervated muscle.