Muscular Dystrophy: Evidence for a Neural Factor

MUSCULAR dystrophy is a group of inherited diseases of man and animals, characterized by degeneration of skeletal muscles. The condition is usually thought to result from a primary biochemical abnormality of the muscle fibres themselves, but several reports have drawn attention to abnormalities in the motor innervation of dystrophic muscles. In human dystrophies, of either the pseudohypertrophic (Duchenne) or the myotonic types, these findings have included the presence of motor end plates with abnormal appearances1, impaired neuromuscular transmission2, muscle fibre fibrillation potentials3 and diminished motor nerve conduction velocities4 (but see Henricksen5). In the dystrophic mouse there have been reports of abnormal looking end plates6, miniature end plate potentials that were either small7 or reduced in frequency7, and fibrillation potentials9. Moreover, McComas and Mrozek10 have shown that approximately a quarter of the fibres in dystrophic mouse muscle are functionally denervated. In the past, many of these findings have been attributed to secondary changes in the motor nerve cell, particularly in its terminal parts, following muscle fibre degeneration.