Eulenburg thus sums up the relations between progressive muscular atrophy and pseudo-hypertrophic paralysis: In both diseases the fundamental muscular lesion consists in a chronic irritative process, which starts from the interstitial connective tissue, and secondarily affects the muscular fibre. In children, pseudo-hypertrophy of the muscles of the lower extremities is regularly followed by primary atrophy of many of the muscles in the upper half of the body, and secondary atrophy in almost all. In a case of Eulenburg's the two typical diseases seemed to coexist in the same patient, an adult woman. More frequently they coexist in the same family, as in the observation by Russel, where two brothers suffered from progressive atrophy, a third from pseudo-hypertrophic paralysis.
Pick82 relates a case where a typical atrophy of the upper extremities and of the trunk was accompanied by moderate hypertrophy of the calves, with proliferation in the calf-muscles of the interstitial fat and connective tissue. Charcot admits a special form of atrophia musculorum lipomatosa which complicates progressive muscular atrophy, and is associated, therefore, with atrophy of the anterior ganglion-cells; with which, however, it has no direct connection.
82 "Ueber einen Fall von progressive muskel atrophie," Archiv für Psych., Bd. vi., 1876.
The adult and infantile muscular diseases differ by the remarkable, and sometimes even colossal, apparent development of the calf-muscles through the excessive development in them of fat and connective tissue—by the fact that the latter disease invariably begins in the lower extremities, and is almost peculiar to childhood, while the progressive atrophy begins in the upper half of the body, and usually the hands, and is as nearly exclusively limited to adult life. For both diseases may be admitted, with Friedreich, "a congenital nutritive and formative weakness of the striated muscle-substance" (Gowers). But, we may add, in progressive atrophy this does not become manifest until the muscles have been for many years subjected to the strain of constant employment: in pseudo-hypertrophy the nutritive failure appears early in the flagging of the developmental forces at the moment that these are strained in muscular growth.
It would perhaps be more correct to ascribe the error of development to a perversion of nutritive forces rather than to their weakness. For there is no arrest in the general development of the limbs, such as occurs after infantile spinal paralysis: the bones grow normally; the initial lesion is hyperplasia of the connective tissue—possibly, also, true hypertrophy of the muscular fibre. The wasting is secondary. Perhaps the terminal nerve-plates, or else the capillary network on the outside of the primitive bundles of muscle-fibre, does not grow in proportion to the increasing mass, and therefore becomes insufficient for its nutrition (Auerbach).
The question arises whether the primitive error of development does not lie in the capillary network. Ranvier has shown that the capillaries of muscles are specially adapted to them, being disposed in quadrangles, at whose corners the vascular canal dilates into little pouches. It is surmised that these pouches serve as reservoirs to hold an extra supply of blood for the moment of contraction.83 If such specialty of structure be necessary for the proper accomplishment of the muscular contraction, it is evident that any congenital defect in the arrangement of the blood-vessels might disturb in many ways the balance of muscular nutrition. The absence of vascular reservoirs, for instance, would render the supply of blood during the contraction insufficient: the contraction must then be inadequate or exhausting, and the physiological stimulus to the growth of the muscle wanting. On the other hand, the capillaries being, by the hypothesis, adapted to the lower type which nourishes connective tissue, this would become nourished at the expense of the contractile fibre, and the known hyperplasia would result.
83 Cours d'Anatomie au Collège de France, 1880.
That morbid vascularization exists, is shown by the peculiar mottled appearance of the skin, which has often been interpreted as a proof of vaso-motor paralysis (Duchenne). On such an hypothesis, further, the curious and otherwise inexplicable relations between pseudo-hypertrophy and hæmophilia84 would be explained. The one or the other hereditary disease would be due to imperfection in the blood-vessels—here of structure, there of architecture. This imperfection could be directly traced to the mesoblast in the embryo, in which the vascular tissues exclusively originate. Whether we should admit the bold speculation of His85 that the tissues of the mesoblast are exclusively derived from the ovum, while the archiblastic tissues—the nervous, muscular, epithelial, and glandular—come from the substance of the spermatozoa fused with it, is beyond the scope of this paper to discuss. But were this speculation well founded, the independent morbid tendencies of the mesoblast would be rendered by so much the more plausible.
84 Part of which do not exist between pseudo-hypertrophy and progressive atrophy, since the latter disease is not exclusively inherited through the mother.
85 Unsere Körper Form.