Myasthenia

MYASTHENIA (myasthenia gravis pseudo-paralytica, syn.: asthenic bulbar paralysis, asthenic paralysis, amyosthenia, Erb's disease), severe muscle weakness with a picture of pseudo-paralytic phenomena. The etiology of M. has remained unclear to this day. All attempts by various authors to find a patho-anatomical substrate of this disease in the central nervous system or in the muscles have not met with success. Findings occasionally encountered at autopsy do not differ in any definiteness or typicality either in terms of localization or in terms of the nature of the patho-process, and in their insignificance often do not correspond at all to the severity of the suffering. In this sense, autopsy data regarding the central nervous system have to be regarded as devoid of pathogenetic significance. In addition to these non-characteristic changes in the nervous system in M., the presence of so-called "lymphagia" (Buzzard and others) in the muscles has been repeatedly noted, i.e., round-cell infiltration, either limited or diffuse. The majority of authors did not link M. directly to these phenomena and saw in them only an expression of some intoxication process existing in the organism. Only some placed them in connection with the presence of thymus persistens in such cases and attempted to explain the entire myasthenic symptom complex by this. Later, however, it was established that the small-cell infiltration in M. does not have a strictly constant character and does not constitute its specific peculiarity, and that moreover in M., besides the thymus, disorders in the activity of other endocrine glands, for example, the thyroid and adrenal glands, are often noted. Unfortunately, nothing is still known about the state of the autonomic nervous system in M., since all attention in patho-anatomical research is usually concentrated either on the cerebrospinal nervous system or on the muscles; meanwhile there are many grounds to assume that the autonomic nervous system plays a major role in the pathogenesis of M. In favor of this speaks first of all the presence of disturbances of metabolism, both organic and salt, the frequent participation in the clinical picture of phenomena from the internal secretion glands and organs with smooth muscle, and finally peculiar changes in electrical excitability. Some confirmation can also serve the fact that almost all characteristic features of M. were recently noted by many authors as symptomatic phenomena in epidemic encephalitis as a consequence of damage to the autonomic centers. In the clinical picture of M., motor disorders stand first, manifested in constant muscle weakness of a greater or lesser degree and pathologically rapidly occurring muscle fatigue ("apokamnosis") both during their active activity and during contraction induced by means of electric current. In both cases of muscle contractions, initially performed more or less satisfactorily, upon further repetition they decrease in volume and strength, and soon the muscle reaches complete exhaustion. No less peculiar is the ability of the muscular apparatus to recover quite quickly and be ready to give new motor reactions, although of lower intensity than before. One of the most characteristic indicators of this type of fatigue is the so-called myasthenic electrical reaction of muscles to faradic current, giving a clear picture of gradual exhaustion of muscle activity (see figure). The study of muscle contraction curves in M. using graphic methods upon stimulation of muscles with electric current showed that contractions often already from the very beginning have a weak and flaccid character ["myobradia" according to the terminology of Rautenberg]. Muscle weakness leaves a peculiar imprint on the patient, manifested in his external appearance, in his flaccid, little mobile facial musculature, in his manner of performing certain movements. In cases of more pronounced severity, the face acquires a special expression due to the drooping of the upper eyelids and an asthenic, and sometimes even paralytic state of the mimetic musculature. Often at the same time speech is disturbed—it becomes indistinct, dull, with a nasal shade, especially during prolonged conversation. The cause of these fluctuating in intensity speech disturbances depends on the asthenic state of the musculature participating in the act of speech. Sometimes simultaneously disorders of chewing and swallowing are noted. Thus the bulbar symptom complex is outlined here, which served old authors (Erb, Goldflam, Oppenheim) as a starting point for constructing the clinical picture of M. and gave occasion to call the latter asthenic bulbar paralysis. Soon, however, in M., besides bulbar symptoms, a whole series of symptoms of cerebral and spinal origin were noted, which significantly expanded its clinical picture; nevertheless, M. remained, as before, a disease linked exclusively to disorders of the activity of striated muscle. Within these limits, Oppenheim outlined it in 1901 in his work "Die myasthenische Paralyse." In the subsequent period, cases increasingly often appear in the literature which do not fit into the previous clinical picture. Along with the participation of striated muscle in the main process, the participation of cardiac and smooth muscle, as well as the endo-autonomic system, began to be noted. New features were noted in the very nature of the damage to the musculature. Around 30 cases of M. with muscle atrophy, sometimes quite significant, usually without regeneration reaction, but with peculiar changes in electrical excitability, indicating temporary disturbances of neuromuscular activity, have been described by a number of authors. At the same time, a series of reflex disorders was observed in the form of exhaustion not only of tendon, but also of pupillary reflexes. In isolated cases, disorders were noted on the part of the senses and psyche in the sense of rapid fatigue, as well as sleep disorders. All this material accumulated over the last 25 years clearly shows that M. goes far beyond purely motor disorders and represents a disease with a broader basis, in which the autonomic nervous system takes the leading part. The diagnosis of M. in typical cases does not present great difficulties. M. differs from progressive bulbar paralysis by the instability of the clinical picture, a tendency to remissions, whereas the latter is characterized by gradual increase of symptoms, as well as the presence of true paralysis with regeneration reaction in the muscles. Acute bulbar paralysis differs from M. by apoplectic development and obvious involvement of the vascular system. In neither of these diseases is the characteristic for M. fatigue observed, but paralysis is present. It is much more difficult to draw the boundary between M. and encephalitides of various natures. The latter are characterized by acute onset, rapid development of the clinical picture, greater persistence of symptoms, usually increased temperature, and sometimes general cerebral phenomena. The prognosis of the disease is unfavorable in most cases. The disease, however, can drag on for a long time if no complications appear in connection with bulbar disorders. There is no rational therapy whatsoever. As symptomatic treatment, general strengthening agents, strychnine preparations, and light massage are applied.