Sometimes these methods of applying heat increase the pain, and they should not then be persisted in, otherwise a neuralgia may be changed into a severe neuritis, or if the pain is due to a neuritis in the first instance it is almost certain to be aggravated, especially when the affected nerve is superficial.
The heat from a Bunsen burner, as in the Tallermann apparatus, may be used on a single limb when electric heat is not available and a tempera ture of 300° F. (548° C.) can be safely borne.
Cold applications, as Ice, freezing with Ether or Ethyl spray, Carbonic Snow or Liquid Air, are seldom well borne, but they may be tried when heat fails.
Local anodyne drugs have been applied to the skin over the affected nerve, and when this is very superficial considerable relief may follow. Thus Menthol, Aconitine or Aconite, Belladonna or Atropine, Chloroform, Veratrine, Chloral Camphor, Radium emanations, Thorium, Guaiacol, &c., have all been employed. The following formula combines several of these, and it may be painted on the skin over the pained nerve : It. 01. Illeatha? Pip. 5vj.
()I. Caryophylli 5ij.
Chloroform): 5ij.
Linim. Aconiti 5vj.lisce Kataphoresis.—Electric Osmosis or Ionic Medication is now extensively resorted to in order to cause certain anodyne substances to penetrate the unbroken skin, which under ordinary circumstances offers an effective barrier to absorption. The electrolytic drug in solution is placed upon the skin and a galvanic current passed through it to dissociate its opposing " ions,'' which are carried through the skin and reach the affected nerve terminals. The base appears at the negative pot& or kathode; the acid radical is attracted to the anode. Excellent results have been obtained in facial and other neuralgias by applying the negative pole over the skin moistened with Sodium Salleylate solution; the positive salicylic ions are driven inwards. Cocaine, Morphine, Aconitine, Atropine and Quinine arc applied under the positive pole, like all metallic substances. A current commencing with 5, increasing to 3o, milliampixes should be employed and so manipulated by gradually turning it on and switching it off after about 3o minutes' action that no shock need he felt.
Hypodermic or deep parenchymatous injection is employed for the local effects of such drugs as Cocaine, Morphine, Atropine, Chloroform, Ether, Alcohol, Antipyrine, Menthol, Guaiacol, Osmic Acid, &c. When Water alone is injected the method is known as Aquapuncture.
Alcohol has been injected with marked success in severe tic douloureux; or 2 c.c. of 8o per cent. alcohol produce considerable pain of short duration when injected into the affected nerves; this is followed soon by anaesthesia which lasts for several days; usually many months' and in some cases several years' respite is obtained. Stewart employs the solution recom
mended by Patrick and Hecht, which consists of 3 drs. absolute alcohol, dr. water, i gr. cocaine hydrochloride and io mins. chloroform. The injection is made with a specially devised strong needle containing a blunt stilet, which is pushed home after the skin has been punctured with the needle.
The supra-orbital division of the nerve is operated upon as it emerges through the sphenoidal fissure by entering the needle at the outer margin of the orbit, and pushing it home for about 11 inches; the third division is attacked at the foramen ovule by thrusting the needle deeply through the check behind the last molar and guiding it upwards and backwards till the base of the pterygoid plate is reached. The second division is injected as the nerve emerges through the foramen rotundum by entering the needle posterior to the lower border of the zygoma till the floor of the pterygo maxillary fossa is reached.
The injection is usually repeated upon the second and third days and in some cases at later periods, a dozen being usually necessary for a course.
Osmic Acid (i per cent. solution) has been injected in exactly the same way as the alcoholic solution, the nerve being reached in the bony openings as it leaves the skull. The writer has used this acid for deep injection into the sciatic with great advantage.
Cautery is a favourite with some practitioners; every shade of intensity of action can be gauged by regulating the temperature of the metal and the pressure with which it can be applied to the skin. Thus the actual cautery may be dipped in very hot water and applied directly over the tender points or over the trunk of a painful nerve, when it may afford relief without injuring the skin. Dipped in boiling water or heated gently over a spirit lamp a mild dermatitis can be pro duced by permitting it to remain for a few seconds. At a dull red or even at a bright red heat it may be rapidly drawn across the skin like a pencil so as to very lightly scar the superficial layer, or it may be pressed for a few seconds at various points along the course of the nerve so as to pro duce a series of eschars. This method is very satisfactory in intercostal neuralgia and in intractable cases of sciatica. The Paquelin cautery may be also employed in these various ways, but the clectro-cautery causes too severe a destruction of tissue to be manageable.