Cases of hypertrophy, calves, thighs, glutæi, and sacro-lumbales muscles: Duchenne (1st, 5th, 6th, 7th, 8th, 12th, the last being the miniature Hercules, in which all the muscles were hypertrophied except the pectorals), Heller (2 cases), Benedikt (1st, 2d, 3d, 4th; in the 5th the sacro-lumbales atrophied), Gowers (13th, 20th), Pekelharing.
Cases with hypertrophy of the calves and glutæi, with atrophy of the thighs: Berend, Duchenne fils (hypert. sacro-lumbales), Duchenne (3d, 4th, 10th).
Cases of atrophy of all but calves: Spielmann, Gowers (7th), Hammond (2 cases).
Cases of hypertrophy of calves and deltoids, atrophy of all other muscles: Ross (2 cases).
The flexor muscles of the leg are much less often affected than these; the adductors and the ileo-psoas rather more frequently. Paresis and moderate hypertrophy of the abdominal muscles, though relatively rare, are observed. Thus, from the foot up to the spinal column the morbid imminence is pronounced on the side of the extensor muscles. The liability to invasion on the part of the flexors is greatest at the foot, where dorsal flexion is early impeded, and diminishes upward toward the abdomen.
Most important for the theory of the disease is the fact that the hypertrophic appearance of the muscles is never accompanied by even a transitory period of increased strength.28 Some degree of paresis usually precedes the hypertrophy, and becomes intensified when this sets in. The two symptoms, however, are by no means proportioned to one another.
28 In Auerbach's case of true muscular hypertrophy the same paresis was observed.
There is another anatomical change in the muscles no less characteristic of the disease than is their hypertrophy, which contributes at least as much to the loss of muscular power. This is atrophy of the muscles, which in the lower extremities is almost invariably secondary to a stage of hypertrophy, but which occasionally in the quadriceps extensor constitutes the primary lesion. On the other hand, the calf-muscles, though occasionally retroceding from a state of exaggerated hypertrophy, never atrophy below the normal dimensions.29
29 Hammond relates a remarkable case where the muscles of the calves and thighs, having enlarged progressively during about two years, then began to waste, and continued to do so for three years. Then a second stage of hypertrophy set in, and continued at the time of writing (Treatise on Nervous Diseases, 6th ed., p. 508).
It not unfrequently happens that the atrophic and hypertrophic processes go on simultaneously in the same muscle, and so compensate each other that the muscle varies little or nothing from the normal size. This is especially apt to be the case with the pelvic and lumbo-spinal muscles; and thus functional disturbances will develop for which the mere appearance of the involved muscles seems to furnish no sufficient explanation.