Seidel has also examined the temperature of the diseased muscles during their contraction either under the influence of the will or of the faradic current. The hypertrophied gastrocnemius muscle showed a rise of 1.5° to 2° less than a healthy gastrocnemius similarly excited. The rise of temperature never occurred during the contraction, but during the ten or fifteen minutes which followed it. The duration of this rise of temperature was always longer than in the control experiment performed on a healthy subject. The observation was the same in hypertrophied and in atrophied muscles, and indicated a notable diminution of heat-production in both.42
42 Loc. cit., p. 54.
The mental functions are not unfrequently impaired. The defective intelligence exhibited by several of his first patients led Duchenne to attribute a cerebral origin to the disease. The internal hydrocephalus discovered at the autopsy of the case so recently published by Pekelharing suggests that this hypothesis may have been too hastily abandoned, and that it may really prove to be correct for certain cases. In many, however, the intelligence is intact or even precocious, and all suspicion of cerebral lesion must be excluded.
COURSE OF THE DISEASE.—As already stated, a period of paresis may precede all signs of hypertrophy for several weeks, months, or even years. From the time that the enlargement of the calves has once begun about a year and a half is required before the maximum of hypertrophy is attained. Then the disease usually remains stationary for two or three years before the third period is ushered in by aggravation of paralysis in the lower and by extension of paralysis, together with hypertrophy or atrophy, to the upper limbs.
When, from complete loss of muscular power, the patient has become permanently condemned to a recumbent position, life may nevertheless be prolonged for ten or twelve years, with integrity of all the vegetative functions. Death finally takes place, in all recorded cases, from some acute pulmonary disease, whose effects are intensified by the atrophy of the external respiratory muscles, which often extends even to the intercostals.
The course of the disease, and consequent prognosis, is much modified in the rare cases in which it attacks girls. Two of Duchenne's thirteen cases were girls: in one the disease was spontaneously arrested, in the other apparently cured. Lutz43 relates the altogether exceptional history of a family in which five female members were affected—two sisters, also one step-sister, daughter of the mother by an earlier marriage, a sister and niece of the mother, of whom a brother also was diseased. The step-sister and niece both died at six years of age, but the aunt lived to be forty-three (the brother to be forty-two), and one of the girls observed by Lutz, who began to suffer at the age of six, was twenty-eight at the time of observation: paresis had only become marked at seventeen, and locomotion impossible at twenty-two. In the other girl the first symptoms appeared at seventeen, and at twenty-two were still moderate and confined to the lower extremities.
43 Deutsches Archiv f. klin. Med., Bd. iii., 1867.
In Roquette's female case44 the disease began at ten; in Hoffman's,45 at eleven and a half. These cases, with one of Benedikt's, are the only female cases among the 88 I have analyzed.46 Gowers estimates 30 female cases out of a total of 220, or only 13 per cent. of the whole.
44 Inaug. Dissert., Berlin, 1868, quoted by Friedreich.