Amyotrophy

AMYOTROPHY [from Greek a- (negative prefix), mys (myo)-muscle and trophe-nutrition], a general concept for designating any form of muscle wasting and atrophy. The causes of A. are various: diseases of muscular tissue, the nervous system, joints, etc. Diseases of the muscles that cause amyotrophy can be acute (polymyositis) and chronic. The latter include various forms of muscular atrophy (myopathies ^familial, degenerative, etc.). Diseases of the nervous system very often manifest as A. (cerebral, spinal, peripheral); in addition, A. can also develop in disorders of the autonomic nervous system due to direct disruption of trophic innervation (autonomic amyotrophy) and in neuroses (muscle wasting due to inactivity, lack of movement). A. depending on organic diseases of the nervous system can be called neuropathic A. In diseases of the joints, extremely severe A. can be observed, mainly due to reflex effects of the joint disease on the trophic innervation of the muscles (these reflex amyotrophies are similar in their pathogenesis to Sudeck's bone atrophy); it is possible that here A. is a consequence of the direct action of infection on the muscles, on the nerve apparatus, vessels, and that the absence of movement affects the nutrition of the muscles. For reflex muscle wasting, the characteristic feature is the relatively rapid development of A. A. also develop as a result of general infectious diseases and exhaustion. The patho-anatomical picture in A. varies depending on the nature of the process and its pathogenesis. In acute muscle diseases, there is a picture of inflammation with all its characteristic data (acute myositis or polymyositis). In chronic A.-picture of thinning of muscle fibers, reduction in their number; in cases of A. with some hardening of the muscles, development of connective tissue, increase in sarcolemma nuclei, thinning of muscle bundles, disappearance of sarcoplasm are noted. Individual features of the patho-anatomical picture may be typical for separate diseases. The question of the pathogenesis of A. is quite complex, depending on various (central and peripheral) diseases of the nervous system. (For innervation of muscles and trophic influences, see Trophic disorders.) The most essential feature in the picture of A. is the relationship to excitability from the side of the muscle. If the reaction of degeneration is established, then undoubtedly we are dealing with A. depending on the lesion of the peripheral neuron, i.e., the nerve cell of the anterior horns of the spinal cord or its axon-cylindrical process, innervating the muscle fibrils. This type of degenerative A. is observed in diseases of the gray matter of the spinal cord (acute, subacute, chronic poliomyelitis, amyotrophic lateral sclerosis, syringomyelia or gliomatosis, hematomyelia, tumor, etc.), of the anterior roots of the spinal cord (meningitis, tumor, spondylitis, etc.), of the peripheral nerves (neuritis, polyneuritis). If there is no degenerative amyotrophy, then muscle wasting depends on one or another muscle disease, disease of the brain, autonomic nervous system, or other causes. A. can undergo reverse development (even in cases of degenerative picture), or progress, especially in cases of muscular dystrophies (myopathies) and amyotrophic lateral sclerosis, or remain in the same state. The best therapy for A.-massage and electrotherapy; good nutrition and appropriate function of the muscle (gymnastics, movement, work) are very important. In preventive terms, it is very important to consider the possibility of developing A. in various diseases (sequelae of infantile paralysis, spinal and other diseases).