There is no need to dilate at greater length upon the varieties in the symptoms of myalgia, according as it affects one or another part of the body. We must consider, briefly the different kinds of cause that produce it. The immediate source of the pain being, as we have seen, the sense of embarrassment in a muscle obliged to contract when unfit for the work, we have to ask what are the remoter causes that can produce this special unfitness for the work of contraction. They are three: (a) Overlabor pure and simple (i. e., in proportion to the existing bulk and quality of the muscle); (b) cold, and especially damp cold, producing a semi-paralyzing effect on the vaso-motor nerves, and causing congestion and sometimes a little effusion among the fibres or within the sheath of the muscle; (c) fatty degeneration of muscle which is exposed to inevitable and incessant work. Either of these conditions may so disable the muscle that its unavoidable contractions will set up the myalgic state.
Undoubtedly however there is something further, in the shape of a natural predisposition not yet understood, which makes some patients so much more liable to suffer myalgic pain as a consequence of this sort of influences than other persons are. I am in no condition to decide what the nature of this predisposition is; I feel sure it is heightened by an inherited or acquired gouty taint, but I have seen it in people whom there is no reason to suspect of gouty tendencies. It appears to have no connection with true rheumatism.
Still after all that can be said, myalgia remains a disease chiefly of local origin, and depending for nine-tenths of its causation upon a derangement between the balance of work and nutrition in the muscle.
As regards the diagnosis of myalgia from neuralgia, which is a very important matter, the following are the main points that we should recollect:
| Neuralgia. | Myalgia. |
| Follows the distribution of a recognizable nerve or nerves. | Attacks a limited patch or patches that can be identified with the tendon or aponeurosis of a muscle which, on inquiry, will be found to have been hardly worked. |
| Goes along with an inherited or acquired nervous temperament, which is obvious. | As often as not occurs in persons with no special neurotic tendency. |
| Is much less aggravated, usually, by movement than myalgia is. | Is inevitably, and very severely, aggravated by every movement of the part. |
| Is at first accompanied by no local tenderness. | Distinguished from the first, by localized tenderness on pressure as well as on movement. |
| Points douloureux, when established at a later stage, correspond to the to the emergence of nerves. | Tender points correspond to tendinous origins and insertions of muscles. |
| Pain not materially relieved by any change of posture. | Pain usually completely and always considerably relieved by full extension of the painful muscle or muscles. |
The treatment of myalgia is not only satisfactory in itself, but often affords, in its results, a very desirable confirmation of diagnosis.
For a very large number of cases, all that is required is (a) to put and keep the affected muscle in a position of full extension, which is only to be changed at somewhat rare intervals; (b) to cover the skin all over and round it with spongio-piline, so as to maintain a perpetual vapor-bath; (c) on the subsidence of the acutest pain and tenderness, to complete the treatment by one or two Turkish baths, to be taken in the manner that I have recommended by speaking of the prophylaxis of neuralgia.
When treatment such as this cures a pain which was greatly aggravated by muscular movement, we may be sure that pain was myalgic and not neuralgic.
The pain, however, is not unfrequently rebellious to such simple remedies as these, more especially when (as in pleurodynia) we are not able to enforce complete physiological rest of the part. When this is the case, we shall find the internal use of twenty and thirty grain doses of muriate of ammonia by far the most effective remedy. In the first very acute stage of a severe case it may be advisable to inject morphia hypodermically; but this is seldom necessary. The muriate-of-ammonia treatment may be usefully accompanied by prolonged gentle frictions, three or four times a day, with a weak chloroform liniment.