The distinctive clinical course of SMA, characterized by slowing of the rate of degeneration
with the passage of time, presents a special challenge to therapeutic clinical trial planning.
Much of the actual functional decline may represent either an inevitable consequence of
growth or the result of various secondary complications of weakness, making the study of
agents intended to improve the course by increasing the level of SMN protein that much
more difficult. Studies intended to demonstrate a slowing of the rate of degeneration …