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

by Unknown

If we add to these considerations the fact that the symptoms are best explained by such a view, little more seems required to establish it. Recalling the well-known observation of Waller, confirmed by Bernard and others, that after section of the anterior root of a spinal nerve the distal end wastes, while the central end remains intact, because it is still connected with its own trophic centre, we have in this the explanation why atrophy of the anterior roots is also so common a symptom in progressive muscular atrophy. The fibres of the anterior roots arise from the cells of the anterior cornua, and disease of the latter must unfavorably influence the nutrition of the former; hence their atrophy. This atrophy of motor nerve-filaments is continued into the mixed nerves distributed to muscles, but is less easily demonstrable by reason of the gradually diminishing size of the nerve-trunks and by the fact that they are united in the mixed nerve with the sensory fibres from the posterior roots, which do not suffer atrophy. In consequence of the degeneration of these nerves follows degeneration of the muscles to which they are distributed, so that the alterations in the latter are altogether secondary.

From this point of view the disease in question is to be regarded as a chronic form of poliomyelitis anterior, while the essential infantile paralysis of Rilliet and Barthez would correspond to the acute form of the disease.

The association of changes in the anterior roots with others in the spinal cord may be explained either on the ground of extension by continuity to adjacent parts, or on that of coincidence. In illustration of the latter I may refer to a case recently reported from Mendel's clinic²⁵ in Berlin, in which the symptoms of progressive muscular atrophy were associated with those of tabes dorsalis or progressive locomotor ataxia. Here it is not unlikely that the coincidence is merely accidental; and this was Mendel's opinion in this case. In other instances the involvement of other portions of the spinal cord may be a result of an extension of the disease from its true seat, while many cases described as progressive muscular atrophy are not such at all, but are in part the result of other affections of the spinal cord. It is evident, also, that this order may be reversed, as in a case reported by Eulenburg²⁶ to the Berlin Medical Society.

²⁵ Philada. Medical News, Sept. 12, 1885, p. 188.

²⁶ Berliner klin. Wochenschr., No. 15, April 13, 1885.

SYMPTOMS.—The first distinctive symptom of the disease under consideration is the muscular atrophy or wasting. However general it may subsequently become, it is at first localized. The upper extremity is by far the most frequently involved—7 out of 9 times in Aran's cases. Sandahl out of 62 cases found the right upper extremity attacked 37 times, the left in 14 instances, and both in 11. In Friedreich's statistics it occurred first in the upper 111 times out of 146, while the lower was invaded 27 times, and the lumbar muscles 8. Most frequently it begins in some muscle or group of muscles in the right hand, either the interossei or those of the ball of the thumb. Of the interossei, the external interosseus is usually the first affected. Thence it extends to the other interossei, and soon very striking depressions make their appearance between the metacarpal bones, and the extensor tendons on the dorsum, and the flexors in the palm become as distinct as if dissected out. Succeeding this follows contraction of the flexor tendons until the picture seen in Fig. 32 is produced, in which 1 exhibits the anterior surface of the hand, and 2 the posterior.

FIG. 32.

(1) HAND, PALMAR SURFACE. (2) DORSAL SURFACE (after Duchenne). a, Ends of the metacarpal bones; b, Tendons of the flexor sublimis; c, Muscles of the ball of the thumb.

Opinion is not unanimous as to whether the atrophy when beginning in the hand involves first the thenar muscles or the interossei. Roberts, Wachsmuth, and Friedreich say that it begins, as a rule, in the thumb; Eulenburg, that it invariably begins in the interossei. From the interossei it may creep up the forearm, and thence to the arm, or it may skip the forearm and pass into the arm, although the triceps extensor muscle is usually spared. It may come to a standstill in either of those places, but may involve the muscle of the shoulder, especially the deltoid. When the latter and the arm are involved, a picture like that of Fig. 33 is produced.