Neurogenic disorders affecting muscle: five year analysis of muscle biopsies. II. Myopathic changes

The tissue diagnosis of neurogenic atrophy has long been based on the histologic features of segmental atrophy. Skeletal muscle biopsy interpretation was based on the observation that following experimental denervation, the muscle fibers appropriate to the affected motor unit showed atrophy without structural change. Occasional reports have suggested that some of the observed structural changes indicated an associated myopathy. However in recent years a number of reports have appeared showing that previously considered myopathic changes have not been limited to muscle diseases wholly of myopathic origin. As part of a 5 yr prospective study of muscle biopsies, the presence of structural changes in patients with known neurogenic disease was investigated. A significant incidence of sarcoplasmic structural change existed in neurogenic disorders of muscle. These sarcoplasmic alterations were most commonly of 5 types: floccular change, phagocytosis, basophilia, inflammation, and target for targetoid fibers. Similarly alterations of muscle fiber form were frequently present in both groups. The diagnosis of ''neurogenic atrophy'' does not preclude the presence of sarcoplasmic structural change in muscle. It is suggested that sarcoplasmic changes encountered in neurogenic disorders be accepted as an integral part of the pathological process, and not be given independent ''myopathic'' status.