A system of practical medicine. By American authors. Vol. 4

by Unknown

PATHOLOGICAL ANATOMY AND HISTOLOGY.—Two principal seats of change have been found to exist in connection with progressive muscular atrophy. The first and easiest recognized is, of course, the alteration in muscles; the second, that in the nervous system.

The muscular change is simple, and affords a typical instance of what is known as numerical atrophy. The muscular fasciculi one after another undergo fatty metamorphosis, succeeded by absorption of the resulting fat and substitution of connective tissue. The rate of atrophy varies, but sooner or later the muscle is more or less substituted by fibrous bands and cords, over which may be traced reddish lines which represent muscular tissue in a normal state.

The rationale of these changes has not been always the same. The older observers regarded them as the result of a primary fatty metamorphosis of muscular fasciculi, followed by absorption of the resulting fat. Later it was asserted that the atrophy is secondary to a myositis or inflammation of muscle, beginning as a hyperplasia of the interstitial connective tissue in its finest ramifications between the single primitive fibrils. Along with this are seen the results of irritation in the primitive bundles themselves, shown by swelling and multiplication of the muscular corpuscles, proliferation of their nuclei, and sometimes cloudy swelling. Even hypertrophied muscular fasciculi and dichotomous and trichotomous subdivision have been noted by Friedreich.

It sometimes happens that the hyperplastic process in the intermuscular connective tissue is succeeded by a fatty infiltration of the cells of the connective tissue, and there results a lipomatosis which is invariably outside of the muscular fasciculi and between them. This gives rise to an appearance of hypertrophy which is only apparent, for the muscular fasciculi are themselves wasted, and proportionally paralytic. This is seen to occur particularly in the muscles of the calves of the legs, in which is produced an appearance identical with that in the disease known as pseudo-hypertrophic muscular paralysis, with which, indeed, the condition under consideration is considered by some identical. But although we must admit in certain cases a complication of a certain degree of lipomatosis with progressive muscular atrophy, the two diseases are essentially different; and it is quite likely that in some instances pseudo-hypertrophic muscular paralysis has been mistaken for progressive muscular atrophy.

The changes in the nervous system are not nearly so simple. They have been noted in the peripheral nerves, both in their trunks and in their intermuscular branches; in the anterior roots of the spinal nerves; and in different parts of the spinal cord, including the central gray matter, the antero-lateral and posterior columns; also in the sympathetic system. These nerve-changes are not simultaneous, nor have they been discovered in every case. It is a noteworthy fact, however, that as methods of examination have improved and the manipulative skill of observers has increased the number of negative cases has diminished.

First, as to alterations in peripheral nerves in their ultimate distribution: The character of these is of a kind usually described as irritative; that is, there is a hyperplastic process in the connective-tissue sheaths (neurilemmæ) and their internal prolongations, consisting in nuclear proliferation and thickening of the tubular membrane or sheath of Schwann. Varicose distortion of the medullary sheaths and their subsequent disappearance, together with destruction of the axis-cylinders, also occurs.

The changes in the peripheral nerve-trunks, as studied in the median, ulnar, radial, and musculo-spinal, are essentially the same, resulting in thinning of the diameters of the nerves. These changes, however, are by no means constant.

The anterior roots of the spinal nerves exhibit alterations in a large number of instances. Cruveilhier called attention to them in the celebrated case of the rope-dancer Lecomte. At the autopsy, the brain, the cord, and posterior roots were found normal, but the anterior roots, from the point of exit to where they unite with the posterior, were greatly atrophied. In another case the anterior roots were to the posterior in thickness, in the cervical region, in the ratio of 1:10, while the normal ratio is 1:3; in the dorsal region as 1:5, while the normal is as 1:1½ or 2. The posterior roots, brain, and cord were again unchanged. Up to 1876, Eulenburg had collected 26 cases in which this alteration existed, and 19 in which it was absent. In the case of Wood and Dercum, referred to, this atrophy of the anterior nerve-roots existed, making 27 positive cases and 19 negative.

We come, finally, to the spinal cord as the seat of changes, and we are met by Eulenburg's statistics, according to which, up to the date of his article, there were 34 cases of positive disease and 15 negative. To the former we have again to add the case of Wood and Dercum, making 35 against 15. These alterations are by no means constant as to seat and character. Thus, Valentiner, who seems to have been the first after Cruveilhier, in 1853, to record any, found in 1855, in the centre of the cord, in the neighborhood of the three lowest cervical and upper dorsal nerves, that the elements in the region of transition from gray to white substance were obliterated, and the softened place contained numerous compound granule-cells. Schneevogt also found a softening of the cord from the fifth cervical to the second dorsal nerve, Frommann described a red softening from the medulla oblongata downward, involving chiefly the anterior and lateral columns, and especially the commissures and the innermost parts of the anterior columns lying next the commissure.

Luys found the gray matter in the neighborhood of the cervical enlargement full of hyperæmic vessels, which were surrounded with granular masses (compound granule-cells?). The same granular masses, together with numerous corpora amylacea, were scattered throughout the gray substance. The ganglion-cells of the anterior cornua had almost disappeared in the part affected, and appeared to be replaced by the granular masses. Here and there a few ganglion-cells could be recognized in a state of retrograde metamorphosis, pigmented and bereft of their polar prolongations. In this case the degeneration affected principally the left anterior cornu, and it was the left side of the body which was affected by the atrophy. The anterior roots of the spinal nerves on the left side were also atrophied. Lockhart Clarke found essentially the same changes in no less than six cases, and Duménil, Schueppel, Hayem, Charcot (six or seven autopsies), Joffroy, and lately Wood and Dercum,²³ have added others. The last two observers found changes in the lower portion of the cervical enlargement of the cord, and state in the report of their case that "in the anterior cornua of the gray matter there is a marked diminution in the number of nerve-cells. Of the three groups of these cells, the anterior has almost entirely disappeared, the lateral group is represented by but a few individual cells, while the internal group seems to have undergone a less marked change. All of these cells, with the exception of a few in the internal group, appear shrunken, and are evidently much diminished in size. They have lost in great part their polygonal shape, many of them being fusiform, and present but few processes. Only in the internal group are these cells in any way approaching the normal type, and these are few and seen in only a few of the sections. They present the characteristic size and numerous processes of the typical motor-cell, while they disclose a well-defined nucleus and nucleolus. In the atrophied cells the nuclei can only be distinguished with difficulty.