With regard to the seat of neuralgia, there can be little doubt but that it is in the nerve itself ; but it is equally certain that the part where pain is felt is not always the part diseased. The fact is, neu ralgia of any nerve may be purely the result of irritation reflected from a very distant point of the nervous system. Post-mortem examination throws no light on the state of the nerve, but there is no reason to believe that it arises from an inflamed or congested state of the nerve in which the pain has been experienced.
The diagnosis of neuralgia is not in general very difficult, for even when it does not follow the course of a nerve, it may commonly be distinguished from every other disease by the peculiar character of the pain, its excessive violence during the paroxysm, and the absence of all symptoms of fever and inflammation. It may sometimes be difficult at first sight to distinguish neuralgia from rheumatism, inasmuch as the two diseases resemble each other in some of their most prominent symptoms ; but by observing the following diagnostic signs (derived from the general character of inflammation in all parts of the body), the danger of confounding them may be In rheumatism the pain is continual, as is the case in all inflammations : in neuralgia it is never constant, but is subject to paroxysm and intermissions. In rheumatism the pain is aggravated by the slightest pressure ; in neu ralgia, on the contrary, it is sometimes alleviated by it. To these it may be added that in rheumatism we shall find the usual attendants of inflammation, namely, heat, redness, and swelling; while in neu ralgia (as noticed above) these are rarely if ever present.
Dr. Inman has recently pointed out that a painful condition of the muscles, ordinarily known by the name of cramp, is frequently mis taken for neuralgia. This disease, which he calls myalgia, he says may be recognised : 1. By the pain being hot and burning; 2. By its absence in the morning, and increase during the exertion of the day ; 3. By its seat in some one muscle, and being increased by the move ment of that muscle ; 4. It is the result of unusual exertion of the muscle ; 5. It is relieved by relaxation, or artificial support ; 6. The pulse is unaffected ; 7. The pain of cramp often comes on suddenly during the night. The distinction between myalgia and neuralgia is of importance, as the treatment of the two diseases might be directly opposite.
With regard to the treatment of neuralgia, it would appear quite superfluous to say that it must be regulated by the circumstances of each particular case, if it were not notorious that no disease has been treated more blindly and empirically. When any foreign body presses upon the nerve, or when the pain can be distinctly traced to a carious tooth, the removal of the source of irritation will commonly be sufficient to cure the disease, though the practitioner should be espe cially warned against the danger of confounding neuralgia with the tooth-ache—an error that is not unlikely to occur in some cases of tic douloureux, and one that has often occasioned the loss of several teeth to the patient without any good effect. When (as is sometimes the
case) the disease appears to be occasioned by the irritation arising from an old cicatrix, it will be expedient to try the effect of appli cations to the cicatrix itself—namely, either the nitrate of silver, or the actual cautery, or a blister, or a crucial incision over the part, or even its removal by the knife. And in the same way, when it can be distinctly referred to any other of the exciting causes enumerated above, the removal of that will probably be followed by the disappear ance of the disease. But, as already observed, it very frequently happens that the exciting cause cannot be discovered, and in these cases the treatment must necessarily be in a great degree empirical. When the paroxysms are irregular in their duration and recurrence, perhaps the sesquioxide of iron is the best remedy at present known : it may be given in doses of half a drachm three times a day in twice its weight of treacle. When the pain recurs after certain regular intervals, those medicines which are found to be most efficacious in the treatment of ague may be exhibited with advantage. The disul phate of quina may be given in doses of four or five grains three times a day, though this medicine has sometimes been given in much larger quantities, and Sir Benjamin Brodie mentions one case where the patient took as much as half a drachm daily. (` Local Nervous Affections,' p. 28.) The liquor potassm arsenitis is another excellent medicine which may be employed in this form of disease : the dose 18 at the commencement four or five minims three times a day, which may gradually and cautiously be increased to ten or fifteen. When there are any signs of inflammation present, that the disease may seem rather to deserve the name of neuritis than of neuralgia, it must be treated accordingly, and the usual antiphlogistic remedies, both external and internal, may be employed. In almost every case of neuralgia it will be advisable to exhibit some preparation of opium, both to relieve the pain and also in order to procure the patient some sleep at night, at which time the paroxysm are often much aggravated; and especial care must also be taken not only to prevent the consti pation caused by this drug, but also to keep up a free evacuation of the bowels, as in some cases the disease appears to have been cured by purgative medicines alone.