Inherited Neuronal Atrophy and Degeneration Predominantly of Lower Motor Neurons * *This chapter is reprinted from the third edition because the invited author was unable to meet extended deadlines for revision. A recent review of spinal muscular atrophies by Sabine Rudnik-Schöneborn and colleagues can be found in Myology, third edition, edited by A. G. Engel and C. Franzini-Armstrong (McGraw-Hill, 2004). Several tables from that chapter appear here.