2. Neuralgia from direct violence to superficial nerves is produced by cutting or, more rarely, by bruising wounds. Cutting wounds may divide a nerve-trunk (a) partially, or (b) completely.
(a) When a nerve-trunk is partially cut through, neuralgic pain occurs, if at all, immediately, or almost immediately, on the receipt of the injury. One such instance only has come under my own care, but many others are recorded. In my case the ulnar nerve was partly cut through, with a tolerably sharp bread-knife, not far above the wrist; partial anæsthesia of the little and ring fingers was induced, but at the same time violent neuralgic pains in the little finger came on, in fits recurring several times a day, and lasting about half a minute. Treatment was of little apparent effect in promoting a cure; though opiates and the local use of chloroform afforded temporary relief. The attacks recurred for more than a month, long after the original wound had healed soundly; and, for a long time after this, pressure on the cicatrix would reproduce the attacks. A slight amount of anæsthesia still remained, when I saw the patient more than a year after the injury.
(b) Complete severance of a nerve-trunk is a sufficiently common accident, far more common then is neuralgia produced by such a cause; indeed, so marked is this disproportion between the injury and the special result, that I have been led to infer that a necessary factor in the chain of morbid events must be the existence of some antecedent peculiarity in the central origin of the injured nerve. This opinion is rendered the more probable because the consecutive neuralgia is in some cases situated, not in the injured nerve itself, but in some other nerve with which it has central connections. Two such cases are recorded in my Lettsomian Lectures, [Lancet, 1866], in which the ulnar nerve, and one in which the cervico-occipital, were completely divided; in all three the resulting neuralgia was developed in the branches of the fifth cranial. Here we may suppose that the weak point existed in the central nucleus of the fifth; and that the irritation, or rather depression, communicated to the whole spinal centres by the wound of a distant nerve, first found, on reaching this weak point, the necessary conditions for the development of the neuralgic form of pain, which therefore would be represented to the mental perception as present in the peripheral branches of the fifth nerve. In all the cases which have come under my notice, the neuralgia set in at a particular period, namely, after complete cicatrization of the wound, and while the functions of the branches on the peripheral side of the wound were partly, but not completely, restored. The same obstinacy and rebelliousness to treatment are observed as in other instances of neuralgia from injury.
One of the cases above referred to may here be briefly detailed, as it shows very completely the clinical history of such affections. C. B., aged twenty-four, an agricultural laborer, applied for relief in the out-patient room of Westminster Hospital, suffering from severe neuralgic pains of the forehead and face of the left side. Then pains were felt in the course of the supra-orbital, ocular, nasal, and supra-trochlear branches, and also in the cheek, appearing, there, to radiate from the infra-orbital foramen. They had commenced about three weeks previously to the patient's first visit to the hospital, and about six weeks after the accident which appeared to have started the whole train of symptoms. This was a cutting wound, evidently of considerable depth as well as external size, toward the back of the neck, and so situated that it must have divided the great occipital nerve of the left side: and, from the man's account of the numbness of the parts supplied by the nerve which immediately followed the wound, there could be no doubt that this had occurred. There was no acute nerve-pain, either during the healing of the wound, which was rapid, or subsequently, until more than three weeks from the date of the injury; at this time there was still a considerable sense of numbness in the skin of the occipital and upper cervical region; but there now commenced a series of short paroxysms of pain in the forehead of the same side. These at first occurred only about twice daily, at regular intervals; the pain was not very sharp, and only lasted a minute or two. The attacks rapidly increased in frequency and duration, however, and extended their area. At the time when I first saw the case the pain was very formidable, it recurred with great frequency during the day, but would sometimes leave the patient free for several hours together. The site of the wound was occupied by a firm cicatrix of about a line in breadth and an inch and a quarter in length; pressure on this excited only a vague and slightly painful tingling in the part itself, but severely aggravated the trigeminal pains, or reproduced them if they happened to be absent. The regions supplied by the great occipital nerve were still very imperfectly sensitive. This patient gave me a great deal of trouble. He continued for many weeks under my care, and I can scarcely flatter myself that any of the numerous remedies which I administered internally, or applied locally, had any serious effect in checking the disorder. The subcutaneous injection of morphia gave some relief, as it always does, but this seemed to be perfectly transitory; and, although when the patient ceased to attend the hospital he was decidedly better, I cannot imagine that there was anything in it except the slow wearing out of the neuralgic tendency, very much without reference to the administration of any remedies.
The description of neuralgia from injury would be incomplete without some special words on a variety of this affection which has only very recently been described with that fulness which it deserves. I refer to the pains which are produced by gunshot injuries of nerves, received in battle, of which no sufficient account had been given until the publication of the experience of Messrs. Mitchell, Moorehouse, and Keen, in the late American civil war.3
From the interesting treatise of the above-named writers it appears that not merely is neuralgia of an ordinary type a frequent after-consequence of wounds, but that certain special pains are not unfrequently produced. In the more ordinary instances, pain is of the darting, or of the aching kind; and all writers on military surgery, who have recorded their experience of the results of wounds received in battle, have spoken of affections of this kind, for the most part singularly severe and obstinate, and in not a few recorded instances clinging to the patient during the remainder of his life. These pains may at times leave the sufferer, but they infallibly recur when from any cause his health is depressed, and it is an especially common thing for them to be evoked in full severity under the influence of exposure to cold, and particularly to damp cold.
But the American writers introduce us to another and more terrible neuralgia which is a, fortunately, less frequent result of serious injuries to nerves. They speak of it as a burning pain of intense and often intolerable severity; they believe that it seldom if ever originates at the moment of the injury, but rather at some time during the healing process; and it is especially noteworthy that it is sometimes felt not in the nerve actually wounded, but in some other nerve with which it has connections. After it has lasted a certain time, an exquisite tenderness of the skin is developed, and a peculiar physical change of skin-tissue occurs; it becomes thin, smooth, and glossy. It is a remarkable fact that these burning pains which are so definitely linked with a nutrition-change of skin are never felt in the trunk, and rarely in the arm or thigh, not often in the forearm or leg, but commonly in the foot or hand; and the nutrition changes of the skin are generally observed on the palm of the hand, the palmar surface of the fingers, or the dorsum of the foot; rarely on the sole of the foot or the back of the hand. It is very interesting to remark that these skin-lesions correspond very nearly, not only to those observed in the cases of nerve-injury reported by Mr. Paget,4 in which actual neuralgia was present (though the kind of pain is not exactly specified), but also very nearly with the nutritive changes observed by Mr. Jonathan Hutchinson in a number of cases of surgical injuries of nerves.5 The tendency of neuralgic pain accompanied by nutritive lesions of the skin and nails to seat itself in the hands and feet will be hereafter noted in connection with the subject of the pains of locomotor ataxy and of those produced by profound mercurial poisoning. And it will be seen in the section on Pathology, that very important conclusions are suggested by the coincidence.
Joined with the burning pains, and the altered skin-nutrition, in the cases of gunshot injury of nerves which we are considering, there is nearly always a marked alteration in the temperature of the parts, either in one direction or the other. In the great majority of instances of ordinary neuralgia after wounds, this alteration is a very considerable reduction of the temperature