Myopathy

MYOPATHY (from Greek mys-mouse, muscle and patho-I suffer), primary, or idiopathic disease of muscles, a term that has remained from the time when it was believed that the myopathic process was caused by primary damage to the muscle fiber itself, as opposed to secondary, neuropathic disease of muscles. This concept applies not only to diseases of skeletal muscles but also to visceral musculature; for example, one speaks of myopathy of the heart, myopathy of the cardiovascular system (myopathia cardio-vascularis). Similar myopathic conditions can also be observed in some general diseases, such as osteomalacia, acromegaly, and rickets. The clinical and histological pictures of primary myopathy differ significantly from secondary muscle diseases caused by damage to the peripheral motor neuron (see Dystrophy, dystrophia musculorum progressiva; also Muscle atrophy in diseases of the nervous system). It must be remembered that transitional forms exist between primary and secondary muscle atrophies. Usually, primary M. refers to various forms of pure muscle atrophy (myopathic atrophies), grouped together by Erb under the name of progressive muscular dystrophy (muscular dryness, myopathic dystrophy, dystrophia musculorum progressiva, dystrophia myopathica). To the group of M., Peritz also includes congenital myotonia of Thomsen and myotonic dystrophy. Jendrassik points out that in dystrophy, the issue is a general disease that affects not only muscles but also other tissues. Some describe changes in bones in muscular dystrophy and speak of progressive osteomyopathy (osteomyopathia progressiva). Cases of M. sometimes observed in connection with phenomena from the endocrine glands have led many to seek the cause of these M. in the endocrine glands: in polyglandular disease (Schaffer, Bregmann, Peres, etc.) or in insufficiency of one gland (Peritz). Of particular interest are the works that have appeared in recent years, indicating the enormous importance of the vegetative, resp. sympathetic, nervous system in the pathogenesis of muscle dystrophies. Some (Westphal, Petenyi, etc.) described cases of muscle dystrophies associated with forced movements, others - with akinesia (Hoffmann and others). Based on the localization of dyskinetic disorders in the subcortical ganglia, Westphal admits the possibility of central origin of myopathy. Patho-anatomical studies have found in myopathies changes in the basal ganglia and in the diencephalon (Foix, Nicolesco), in the border column and sympathetic fibers of peripheral nerves (Ken Kur6 and his school). Japanese authors, in turn, found dystrophic changes in muscles after extirpation of various sympathetic sections. They also proved that the content of sympathetic, i.e., Remakovsky fibers, in peripheral nerves varies depending on the muscle, and that muscles of the trunk and pelvic girdle are richer in them than distal muscles. They also found that muscle tone and tendon reflexes are reduced in sympathicotomized muscles, just as in dystrophic muscles, that they also do not show fibrillary twitching and regeneration reaction, and that both types tire easily. In both cases, this state of fatigue is eliminated by adrenaline, which has almost no effect on fatigue of healthy muscles. Kure (Kigyo) accepts 4 forms of M. The first is caused by damage to the end plates of nerves, the second - by changes in the border column and changes in sympathetic, possibly also parasympathetic fibers in the peripheral nerve, the third - by changes in autonomic nuclei in the spinal cord, and the fourth - by damage to the higher centers of autonomic muscle innervation. M. are hereditary-family diseases. The type of inheritance cannot yet be considered precisely established. Both dominant and recessive types are accepted, but also a recessive type linked to sex. Davidenkov concludes that in most cases the type of inheritance is dominant, and in some forms it is simple, in others "limited by sex." Hansen and Ubish, based on their research, believe that progressive muscular dystrophy can be caused by the simultaneous existence of two hereditary dominant factors, each of which individually does not cause the disease.