Repeated denervation and reinnervation of skeletal muscle.

Abstract

THE skeletal muscle in human muscular dystrophy shows marked degenerative changes while the central and peripheral nervous systems usually show no abnormality, apart from cerebral malformation underlying co-existing mental deficiency1–3. In the late stages, there may be some loss of anterior horn cells in the spinal cord4. On the basis of these pathological findings, muscular dystrophy has always been considered to be a primary muscle disease. An inherited abnormality of the Bar Harbor 129 strain of mice shows similar pathological changes in the skeletal muscle and no central nervous system abnormality5,6. Motor end plates are infrequent on the small atrophic fibres of the muscles, however7, and electromyography in these animals shows fibrillation potentials and high frequency discharges similar to those seen in human dystrophia myotonica and denervation8. Other findings suggestive of denervation are the reduction of frequency of miniature end plate potentials9, and the supersensitivity of the muscle to neostigmine and insensitivity to d-tubocurarine10. McComas and Mrozek11 found direct evidence of a proportion of denervated fibres in murine muscular dystrophy.