Muscular Dystrophy: Evidence for a Neural Factor

Abstract

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.