NEURALGIA.
Intermittent or remittent pains, in line of nerve without inflammation, or other structural lesion. Diagnosis: lameness, stiffness of particular muscles having a common nerve. Unnatural position habitual. Pain of inflammation and of neuralgia. No functional change. Rheumatism. Tumors. Causes: lead, rheumatism, gout, auto-poisons, cold, anæmia, reflex. Facial neuralgia, occipito-cervical, dorso-intercostal, lumbo-abdominal, sciatic. Treatment: elimination, of lead, etc.; intestinal antiseptics, tonics, hot water, anodynes, arsenic.
This is characterized by pain paroxysmal, intermittent or remittent situated in the course of given nerves. It must be a pure neurosis and unaccompanied by any specific structural lesion like inflammation, degeneration, atrophy, hypertrophy, tumor or the like. It is therefore manifested subjectively and cannot be easily identified in the lower animals. Nevertheless, Lafosse, Zundel, Genée, and others have recorded cases, their conclusion being deduced from symptoms which were held to indicate nervous suffering in the absence of any structural lesion whatever. A priori one can with difficulty escape the conviction that neuralgia must exist in the lower animals as in man, and the only drawback to its recognition is the difficulty of diagnosis.
The first step in such diagnosis must usually be the presence of lameness, stiffness or indisposition to free movement of some particular muscle or group of muscles deriving their innervation from a particular nerve. Or there may be a particular position habitually assumed such as semi-closed eyelids, drawn back ears, laterally inclined neck which strongly suggests nervous suffering. Next, there must be the exclusion of any appreciable structural cause and especially of inflammation. The three prominent features of the pain of inflammation is that it is aggravated by pressure, it is heightened by movement, and it is accompanied by some decided alteration of the function of the part. If there are at the same time exudation and swelling, inflammation is all the more certainly indicated. In a neuralgic pain on the contrary pressure does not increase the pain: it may even alleviate it: movement of the part may be rather satisfactory to the patient than painful; and the disturbance of function, contractile, secretory, trophic, is not perceptible. There is no local exudation nor swelling to account for the nervous disorder.
The liability to confound the affection with a neuritis more centrally situated, but the pain of which is referred to the periphery of the nerve, is to be obviated by a tracing of the nerve along its course to the nerve centre so as to identify any centre of tenderness, and also by the implication of all the peripheral branches coming off ectal of that point.
Again, rheumatism may be easily confounded with neuralgia, but here the affected nerve and muscle and even the skin over it is liable to be very tender to the touch or pinch, and if at all acute some hyperthermia is present. Like rheumatism, neuralgia shows a tendency to shift from place to place.
Pains due to pressure on the nerves by tumors, aneurisms, and other swellings, are constant, whereas neuralgic pains are marked by remissions and aggravations and even by intervals of complete relief.
Causes. The toxic neuralgias are illustrated by chronic lead poisoning, in which, in man, there are wandering pains like those of rheumatism, and in the lower animals muscular stiffness and contractions which suggest a similar condition. In man, too, gout is a common factor, and in pigs and birds in which this condition exists, stiffness and evidence of suffering may well be at times attributed to a similar cause. How many other forms of chronic metallic poisoning and poisoning by morbid autochthonous products of indigestion are attended by disorders of innervation and nutrition, it is as yet impossible to say. The direct action of cold, an anæmic condition of the nerves, and reflex action from distant sources of irritation are among the other invoked causes. Inflammation in the nervi nervorum is also invoked as a factor, but in this case the symptoms would not accord with the rule given above, since the nerve trunks would be very tender to touch or pressure, and the suffering would be unshifting and shown permanently in the one seat.
Facial Neuralgia. Lafosse and Zundel describe as cases of this kind those in which periodically the horse’s eyes are fixed and shining, the ears drawn back and depressed as in vice, the head at intervals bent on the neck, with plaintive neighing, rubbing the head on the stall and pawing. Those cases of twitching of the head or rapid jerking of the ears in horses, when they have been driven for some distance, and which are relieved by wearing a close net over the nostril or by section of the trifacial nerve at the infra-orbital foramen, manifestly partake of this character.
Cervico-Occipital Neuralgia. Lafosse speaks of this as often mistaken for torticolis, the head being turned to the affected side during the paroxysms. In man this is often a result of cold draughts on the back of the head, and associated with tender points on the course of the nerve, between the mastoid and the median line.
Dorso-intercostal neuralgia causes pain in deep inspiration, and lumbo-abdominal neuralgia develops tenderness in the loins, in one testicle, or in one lip of the vulva according to Lafosse. Diagnosis between such cases and neuritis, spinal disease, and other obscure nervous affections must be very problematical.
Sciatic Neuralgia. This is described by Zundel as causing jerking and lameness in the affected limb, sometimes aggravated and sometimes improved by work and associated with muscular weakness or paresis. Sciatica in man is, however, rarely a simple neuralgia, but partakes rather of the nature of a neuritis, and there is no good reason for supposing that the disease of this nerve in the lower animals is other than an inflammatory condition.
Leclainche after consideration of the testimony adduced, is of the opinion that we still lack absolute evidence of uncomplicated neuralgia in the domestic animals.
Treatment. For toxic cases elimination of the poison is the first consideration. For lead carefully graduated doses of iodide of potassium to carry off the offending agent without increasing its poisonous action must be continued as long as the metal is passed by the urine. It may be followed by a course of strychnia, by electricity, massage and blisters. Gouty subjects may be treated with salicylate of soda, alkalies, or colchicum. The victims of Bright’s disease must be treated for the kidney affection.
Where there has been trouble of the digestive organs, intestinal antiseptics (salol, sodium salicylate, bismuth-salicylate, beta-naphthol) and small doses of arsenious acid will sometimes benefit.
In anæmic conditions a course of tonics (cod liver oil, iron, quinine, nux vomica) are indicated, and, to improve the local blood supply, nitro-glycerine. A rich stimulating ration, currying, an open air life, and sunshine (in summer a run at grass) are called for.
In man with a suspicion of traumatic origin, W. H. Thomson strongly advocates a persevering use of the hot water douche to the parts first affected, the hypodermic use of morphia and atropia, and in case of local anæmia nitro-glycerine every three hours. Where there is a suspicion of inflammation he successfully employs absolute rest, with opium narcotism so as to abolish the pain, for twenty days if necessary. Aconite, antipyrin, acetanilid, phenacetin, exaglin, and gelsemium have their advocates, and may benefit in individual cases. A course of arsenic is often successful, and phosphorus and ergot have each proved of value.