Hydropathy.—Douches and baths of various kinds have doubtless proved of much value in the treatment of neuralgia. The majority of them, however, are difficult of application for the general practitioner, and we confine ourselves to mentioning the tonic and soothing action of the wet pack and of the prolonged warm bath, which should be followed by sponging with cool water, and used under every possible precaution against exposure.
Long-continued local applications of gentle heat (bags of sand or salt, or hot water) are often temporarily grateful, and in the treatment of chronic cases the daily application of hot water or ice-bags to the spine is said to have a good effect. In acute and subacute neuritis, and in those forms of neuralgia in which neuritis plays a large part, such as sciatica, the persistent application of ice-bags along the course of the affected nerve, even for days together, is sometimes of great service. Even where we cannot be sure that neuritis is present, long-continued applications of ice may be of use, but alternations of cold and heat, on the other hand, are usually to be carefully avoided. This treatment is safer in chronic than in acute cases, though it may be useful in either.
Counter-irritation.—A spray of ether may be substituted for ice when only a temporary chilling is desired, for its counter-irritant effect. This has even been used on the face, the eye being protected by some suitable covering, and a good deal of benefit is to be hoped for both from this and from the similar use of chloride of methyl.
Debove27 has found the chloride of methyl, used in this manner, singularly effective in the treatment of sciatica. A considerable and long-continued counter-irritation is thus made over a large surface and without great pain. The neuralgia is said to be greatly relieved and a rapid cure sometimes affected.
27 Bulletin générale de Thérap., cited in the Boston Med. and Surg. Journ., vol. cxii. p. 210.
Counter-irritation is also practised by making applications of cutaneous irritants, such as blisters, mustard, turpentine, chloroform, or of the actual cautery carried in light superficial stripes over the skin, and repeated if necessary at short intervals. As a rule, the counter-irritation is more effective the larger the surface which is covered.
The use of the cautery and of blisters is in place in almost every form of neuralgia where the temporary disfigurement is of no consequence.
Of other cutaneous applications, aconite and chloroform liniments, menthol in substance or in alcoholic solution (drachm j or drachm ij to fluidounce j), aconite and veratrine ointments, are the most useful. A strong aconitine ointment, made with Duquesnet's aconitia and lard (drachm j to ounce j), has been recommended by Webber28 to be used in portions of the size of half a split pea, but, though effective, it needs to be employed with great caution.
28 Nervous Diseases, Boston, 1885.
These applications act in part as irritants, by keeping up a play of sensitive impressions in virtue of the lodgment which they effect in the skin, but also, no doubt, by reducing the sensitiveness of the cutaneous nerve-fibres, and thus removing one source of excitation of the diseased nervous centres. The remarkable temporary benefit sometimes obtained from the instillation of cocaine into the eye in cases of neuralgia of the ophthalmic division of the fifth nerve bears testimony in favor of this explanation.