and fingers are the muscles most commonly thus affected. The weak. ness is usually followed by a well-marked degenerative reaction in the muscles. I have seen several cases which began by such subacute or even acute paralysis of the extensor muscles, first in one arm and soon afterwards in the other; the initial condition closely resembled the paralysis from lead-poisoning, even to the escape of the supinator longus and ext. ossis met. pol. This cause was, however, excluded, and soon the muscles of the shoulder and back presented commencing slow progressive atrophy, followed by wasting of the interossei until a typical state was reached. In another case, the quick loss of power was confined to the extensors in one arm, which were already weak and slightly wasted, most of the other muscles of the upper limbs having been long atrophied. When there is weakness of the legs, without wasting, the onset of this may coincide with the atrophy of the arms, or may succeed it at any interval. In one case five years elapsed, after the arms began to waste, before the legs became weak. It is very rare for the paraplegic weakness to occur first. The chief danger to life is from pulmonary maladies, rendered grave from the weakness of the muscles of respiration. The common complication of bulbar paralysis is another frequent cause of death, either by the interference with swallowing and nutrition, or by the laryngeal paralysis. Less commonly, death results from bedsores and septicemia, or from intercurrent maladies. PATHOLOGICAL ANATOMY.-The wasting of the muscles is as evident after death as during life. They are reduced in size and pale in colour. Sometimes there is little in the tint of what remains to suggest muscular tissue. Parts of a muscle may be hardly distinguishable from adjacent fat. On the other hand, the bulk of the muscle may be dark, and pale streaks in it may mark the position of local degeneration. Under the microscope, the fibres present various changes, and of these four are well defined. (1) There may be simple narrowing of the fibres, without any considerable change in their striation (Fig. 137), although the striae often seem to be further apart than normal, and sometimes the fibrillary segmentation is unusually distinct. (2) Simple fatty degeneration, in which the transverse striation gives place to a granular appearance (Fig. 138), the granules becoming larger and fewer (Fig. 137) until ultimately distinct globules are scattered through the sheath. Where the muscle resembles fatty tissue to the naked eye, the microscope may show only sarcolemma sheaths containing groups of globules. (3) Muscular fibres are seen in which the sheath contains only a clear material enclosing a few fatty globules, and a few transverse striæ, faint, as if fading away. It is probable that this is not the result of fatty degeneration, but of a different process, which has been termed "vitreous degeneration,"—a sort of dissolution of the striæ, indicated by the appearance of such fibres as are shown in Figs. 137, 139, 140. (4) A longitudinal striation develops in the fibre, and at first coexists with the trans verse striation; but ultimately the latter becomes indistinct, and the fibre looks like a fasciculus of longitudinal connective-tissue fibres (Fig. 140). Sometimes, with the longitudinal striation, the fibre presents a transverse striation very much finer than normal, the stria being narrower and nearer together, as if from a division of the sarcous elements." This change may sometimes be seen alone, and 66 FIBRES OF WASTED MUSCLES IN PROGRESSIVE MUSCULAR ATROPHY. FIG. 137.-Narrowed fibres with nearly normal striation; others clear, containing a few fat globules, and a few faint transverse striæ, and some longitudinal striation: large globules of fat lie in the interstitial tissue in front of one narrowed fibre. FIG. 138.-Granular degeneration: a fibre with normal transverse striation presents also indications of longitudinal striation. Increase of nuclei of interstitial tissue. FIG. 139.-Two normal fibres and one presenting the clear homogeneous aspect, with a few fat globules and some faint striation. FIG. 140.-Several fibres similar to that of the last figure, with globules of fat between them. On the right is a fibre which has undergone complete longitudinal striation, the normal striæ having disappeared, so that it resembles the adjacent interstitial fibrous tissue. Other fibres in the same muscle were in intermediate stages of degeneration, some transverse striation coexisting with the longitudinal striation. may be present in only one part of a fasciculus. Thus at one place the number of striae in inch was only seven, while in another region of the same fasciculus seventeen were to be counted in the same space. A tendency to transverse fissuring has also been described, but this is probably artificial. Fatty globules accumulate between the fibres (Fig. 140), accompanied in some cases with granules and masses of reddish-brown pigment. There is often also an increase of the nuclei (Fig. 138), and sometimes of the fibres of the interstitial tissue. Two or three rows of nuclei may lie between the fibres. The capil laries may be dilated and distended. It is very common to see muscular fibres that are much altered side by side with others that present a nearly normal appearance. Ultimately the sheaths become empty, and shrink, and may be scarcely distinguishable from the interstitial fibrous tissue. The peripheral nerves contain many degenerated nerve-fibres, and the terminal branches for the muscles a still larger number. If the nerves are traced up to the cord it is found that the degenerated fibres come only from the anterior roots. These are conspicuously changed to the naked eye, small and grey. They may resemble fine threads of connective tissue, and under the microscope no nerve-fibres may be found in them, or only a few may remain of normal aspect, the rest being in various stages of degeneration, or represented only by their empty sheaths. The degree of affection of the anterior roots corresponds to the wasting in the parts supplied by them. The posterior roots are normal. The spinal cord is often softer than natural at the affected part, and the white substance of the lateral columns may be grey and translucent in aspect, especially in the cervical enlargement. Under the microscope morbid changes are seen in the anterior cornua, and also, in most cases, perhaps in all, in the antero-lateral white columns. The change in the anterior cornua corresponds in its intensity to the origin of the nerves to the most affected parts, and since the latter are usually the arms, the disease is generally most intense in the cervical enlargement. In stained sections the grey matter of the horn is less deeply tinted than normal, but in some parts it may stain more deeply, especially in the circumference of the cornu and the processes of grey matter which project into the white column. Occasionally, larger areas have a dense aspect and stain deeply, but the central part of the cornu is generally pale and wasted in aspect. Most of the large nerve-cells have disappeared; many entirely, while others are repre sented only by small angular bodies. Not a single large cell may be seen in a section which, in a normal cord, would contain a considerable number. Frequently, however, a few large cells can still be seen, but most of these have lost their processes and are more globular than normal. The interstitial tissue is also changed. The nerve fibrilla waste with the cells, and there is an increase of the small, angular, and stellate cells and other connective-tissue elements. The larger vessels are dilated and surrounded by unduly wide spaces, but there is no considerable distension of the capillaries. The cornu as a whole is not usually changed either in size or shape. Similar alterations may be traced through the dorsal region. In the lumbar enlargement, the grey matter may be normal, even when it is much altered in the cervical region; but if the legs are wasted, there are changes similar to those already described. When the atrophy begins in the legs, the disease may be more intense in the lumbar than in the cervical enlargement; but more often any degeneration that exists is slighter, and a larger number of normal or slightly FIG. 141.-A normal anterior cornu for comparison with the next figure. changed cells can be seen. Sometimes certain groups of cells are little affected while others are much atrophied. The degeneration may involve to some exten. the intermediate grey matter between the cornua, but here it ceases; the posterior horn is always normal. There is distinct degeneration of the anterior root-fibres passing from the cornu through the anterior column. A few fibres may remain, but whole fasciculi appear to be replaced by fibrous tissue. There is also degeneration of the fibres of the anterior commissure, in consequence of which it stains much more deeply than normal, in the regions in which the grey matter is considerably diseased. In the white columns there is usually considerable, and often almost complete, degeneration of the pyramidal tracts, anterior and FIG. 143.-Progressive muscular atrophy; degeneration of the anterior cornua and pyramidal tracts. A, medulla oblongata, complete degeneration of the anterior pyramids ▲ P; B, at the upper part of the decussation of the pyramids; D, the decussation of the degenerated fibres; A P, the pyramids, still incomplete. C, cervical, D, dorsal, E, lumbar sections. The degeneration of the anterior cornua is complete in C, but in E a few cells remain, for the most part without processes. In C and D the degeneration of both anterior and lateral pyramidal tracts is conspicuous; in E the anterior tract has ceased, and the lateral tract extends up to the surface of the cord, from which it is separated in C and D by the undegenerated direct cerebellar tract. In C and D the degeneration extends forwards in front of the lateral pyramidal tract, but gradually ceases. The fibres of the anterior commissure are also degenerated. In this case the arms were greatly wasted and flaccid; the legs were paralysed, rigid, with moderate wasting. The muscles of the back were also atrophied. In the arms the weakness and wasting came on at the same time, in the right arm some time before the left. The shoulder-muscles suffered first, but the atrophy quickly spread, and was ultimately extreme in the muscles of the shoulders, forearms, and hands. The dis ease ran a rapid course; death occurred two years after the gradual onset. |