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Primary Progressive Myopathy

atrophy, muscular, nervous, regarded, atrophies, disease, myopathic, lesions and affections

PRIMARY PROGRESSIVE MYOPATHY.

This affection did not outer already complete into nosological nomenclature, but took ground there little by little, being built up by the approximation of elements at first regarded as iu no way re lated to each other. Its history is therefore somewhat complex and has only recently been definitely established. At first the two forms of primary inyopathy which we shall study, namely, the atrophic and the psnmlo-hypertrophic, were regarded as entirely distinct one from the other. This separation was of necessity made at the beginning, for authors could not dream of classing together two affections which objectively were so different. As we shall see later there is on one side a considerable increase in the volume of the muscles—au appar ent increase, it is true, since the hypertrophy is really caused by a proliferation of the adipose tissue—and on the other side a true atrophy, a diminution of volume of the muscular tissue proper. It was very natural, therefore, to describe one disease as an hypertrophy with diminution in power, and the other as an atrophy ; and it was only later that a closer examination of the conditions present allowed of the two affections apparently so dissimilar being brought under one heading.

To Duchenne of Boulogne we owe the first description of the dis ease in question. As early as 1861 this author described an hyper trophic paraplegia of infancy. Its pathogenesis at that time was not well understood, as the affection was referred to a cerebral lesion, but its symptomatology was clearly established. In 1866 Cohnheim and Eulenburg, basing their opinion upon the pathological anatomy of the disease, denied that it was due to any cerebral lesion, and placed it among the purely muscular affections. In another work on Pseudo hypertrophic Paralysis, published in 1868, Duchenue also recognized the non-participation of the nervous system. In 1871 Charcot like wise stated that he had found in this disease lesions of the muscular tissue only.

Primary myopathic atrophy was, as I have said, for a long time confounded with the other muscular atrophies. Even after the works of Duchenne (1849) and Aran (1850) there was little settled as to the nature of muscular atrophies. Many regarded them all as primary, and it was only later, thanks especially to the labors of Luys, Hayem, Vulpian, and Charcot, that we came to appreciate the important part played by the nervous system in many of these affections. But we do not mean by that to assert that all the progressive muscular atrophies should be regarded as of nervous origin. Ley den insists that there is a type of atrophy of purely myopathic origin, and he has described an hereditary form of progressive muscular atrophy.

In this form the atrophy begins in the lower extremities and does not involve the upper. Mains, in 1879, endeavored to bring out the points of relationship between the disease described by Leyden and pseudo-hypertrophic paralysis, and this was the first attempt to bring these two forms closer together. Zimmerlin noted a type in which the atrophy was especially marked in the upper portion of the body, the lower extremities not being attacked until much later. Eichhorst published a case in which the trouble began in the perineo-tibial region. Then in 1882 and 1884 Erb studied a scapulo-humeral form of what he called juvenile progressive muscu lar atrophy, and in his last work he insisted upon the identity of all primary myopathies.

In 1885 Laudouzy and Dejerine, who had already the year pre vious presented to the Academie des Sciences a note on myopathic atrophies, endeavored to establish the facio-scapulo-humeral type, and to distinguish it from the juvenile form of Erb. It is to the last named author that we owe the most recent treatise on this subject. In 1891, having collected and studied all the different cases of atrophy, simple or pseudo-hypertrophic, he marked off sharply the disease to which he gave the name of progressive muscular dystrophy. He demonstrated by microscopical studies that the lesions were always the same whether there was hypertrophy or not, that the evo lution was in all cases identical, and that the apparent increase in size depended entirely upon the greater or less quantity of fat in the sclerotic tissue which had replaced the atrophied muscle.

I have already said that it has been impossible to discover any nervous lesions in any one of these forms constituting this nosologi cal ensemble. We shall see, however, that there is an affection known under the name of muscular atrophy of the type Charcot Marie which resembles in several of its characteristics the myopathic atrophies, but which presents at the autopsy true nervous lesions. This has been regarded by some as an intermediate form between the two classes of atrophy. Perhaps in the course of time we shall be able to refer the myopathic conditions now called essential to some trouble of the nervous system.

It is then, as we have just seen, by a succession of works in no way related to each other that we have arrived at the constitution of a group of primary myopathies. Although it is definitely established now that pseudo-hypertrophic paralysis, as described by Duchenne, and progressive atrophic myopathy constitute but one and the same morbid entity, yet we shall find it more convenient for the sake of clearness of exposition to devote a chapter to each of these clinical varieties.