July 20, 2021 The 'most expensive drug in the world', how it works and the devastating disease it treats . by Judith Sleeman, The Conversation Spinal muscula atrophy causes muscle wasting and loss of control, usually starting in infancy. Credit: Orthopedia/Codman Group , CC BY-NC-SA Babies born with the rare, inherited motor neuron disease spinal muscular atrophy are, without treatment, unlikely to reach their second birthday. When, as a researcher in the 1990s, I ...