Upon this and similar evidence is based the modern doctrine of a neuritis migrans, with centripetal tendencies, upon which it is supposed that a very large proportion, at least, of the urinary, dysenteric, and uterine paraplegias, miscalled "reflex," depend; and it is clear that the application of the word "reflex" in such a case is a grave abuse, tending to produce such confusion of thought and error in practice. In relation to the subject of our own inquiry—neuralgia—it is obviously of the highest consequence to investigate the question whether peripheral irritations, analogous to those which produce urinary paraplegia, are at all frequently the cause of the changes in the posterior roots which produce true neuralgia; for of course an inflammation may be the beginning of an atrophy which may presently exhibit no distinction whatever from one of which the origin was altogether non-inflammatory. I think that there is strong reason for thinking that this is not at all frequently the case. In the first place, all the evidence that exists respecting these centripetal inflammations of the cord is opposed to the idea that, save in the rarest instances, the inflammatory process limits itself to one small segment of the cord. Secondly, the description of the pains that have usually accompanied such inflammations of the cord is considerably different from the strictly localized, frankly intermittent character of a true neuralgia; in fact, all we know of the history of myelitis (except when complicated with a large amount of meningitis) forbids us to suppose that severe pain would be an immediate symptom. But, thirdly, a far more important objection to the theory of an origin in localized centripetal myelitis, the result of a neuritis migrans, is the rarity of motor paralysis as an early symptom, instead of which we ought to find a very distinct history of decided paralysis (much more decided than those secondary paralyses which actually do occur in some neuralgias) of the muscles supplied by the anterior roots of the painful nerve, in every case in which such a peripheral origin could be assumed. Again, the totally feverless commencement of neuralgias, a character which is maintained throughout the progress of the milder cases, is entirely opposed to the idea of a direct connection between myelitis and neuralgia. The superficial appearance of pyrexia is sometimes given by a local vaso-motor paralysis, which makes the neuralgic part, after a long bout of pain, hot and red; but of general pyrexia there is nothing.
Taking every thing into consideration, one is inclined to say that there is a probability that in a very limited number of cases peripheral irritation does cause actual limited myelitis, which escapes recognition at the time, but which issues in an atrophy, the subjective expression of which is actual neuralgic pain. We may well ask ourselves, also, whether there is not some likelihood that a peripheral irritation, which stops short of producing an actual neuritis migrans capable of centripetally exciting a myelitis, may not, by a lower degree of centripetal irritation, give a bias toward certain forms of non-inflammatory atrophy in cells of posterior nerve-roots which are congenitally of weak organization. I am inclined to believe strongly that this does occur. For example, I should explain thus the majority of the peripheral cases of ciliary neuralgia, migraine, etc., that we meet with in poor young needle-women, especially the hypermetropic, who, at an age when they can ill afford the strain, work so constantly and strenuously at an occupation which fearfully taxes the eye.
I would also go farther, and express the opinion that peripheral influences of an extremely powerful and continuous kind, where they occur with one of those critical periods of life at which the central nervous system is relatively weak and unstable, can occasionally set going a non-inflammatory centric atrophy which may localize itself in those nerves upon whose centres the morbific peripheral influence is perpetually pouring in. Even such influences as the psychical and emotional, be it remembered, must be considered peripheral—that is, they are external to the seat and centre of the neuralgia. And there are probably few practitioners of large experience who have not seen a patient or two in whom the concurrence of some unfortunate psychical with some other noxious peripheral influence, the whole taking place at some critical period of life (especially in the years between puberty and marriage), seems to have totally deranged the general balance of nervous forces, and induced morbid susceptibilities and morbid tendencies to some particular neurosis. It is a comparatively frequent thing, for example, to see an unsocial solitary life (leading to the habit of masturbation), joined with the bad influence of an unhealthy ambition, prompting to premature and false work in literature and art. The bad peripheral influence of constant fatigue of the eyes in study may so completely modify a young man's constitution as to make a wreck of him in a very few years, changing him from the state of habitual and conscious health to that of chronic neurosis of one sort or another. And, though it is doubtless on persons with congenital tendencies to nervous diseases that such a combination of bad influences produces its most serious effects, yet there unquestionably are a few persons in whom they appear to entirely generate the neurotic constitution. I have already touched upon the part that misdirected psychical influences, especially religious and other forms of emotional excitement, may play in this unfortunate perversion of the natural and healthy nervous functions, more especially in youth; and need only add, here, that perhaps the most fatal combination of all the bad influences is the melancholy union of highly-strained religious sentiment with peripheral sexual irritation, which is, unfortunately, a too common phenomenon under certain systems of education. The most frequent neurotic consequences of the class of influences which have now been referred to are probably neuralgia—in the form either of migraine, of nervous angina, or of sciatica—or else asthma.
But, if the combination of several such centripetal influences may generate the neurosis unaided, even a single one of them operating powerfully for a long period may produce most serious consequences in those who are hereditarily predisposed. The influence of prolonged fatigue of the eyesight, independently of any special intellectual or emotional strain, was strongly illustrated in my own case about three years ago. I was then engaged upon a piece of scientific writing which demanded no great intellectual effort, but was being done against time, and by working, night after night, many hours by gas-light. My neuralgic (trigeminal) attacks came on with great severity, accompanied by vertiginous sensations of so alarming a kind as to make me fear the invasion of some serious brain-mischief. I broke off all work, and went to the sea-side, but was greatly disappointed to find, for the first few days, that the symptoms were not in the least mitigated. The mystery was soon explained. The weather had been such as to confine me a good deal to the house, and, thinking it would do no harm, I amused myself with reading newspapers and novels. At last I suspected that the use of my eyes in reading was altogether mischievous; I desisted from reading any thing, and in forty-eight hours every symptom had vanished.
Among peripheral influences of a more mechanical kind there is one cause of neuralgia, the force of which has been variously estimated, but which some authors rate as very important, viz.: the influence of the pressure, and especially of the varying pressure, of blood-vessels, or other hollow viscera, upon the trunks of the nerves. We must set aside one such action which is undoubtedly very powerful, as essentially differing from the others; I mean the pressure of dilated blood-vessels, especially aneurisms, when this happens to be exerted upon the ganglion of the sensory trunk. Here there can be no doubt of the mischief; for the pressure, if at all severe, gradually destroys the life of the ganglion, upon which, as was proved by Waller, the nutrition of the posterior nerve-root hangs with very intimate dependence, and the pulsations of the vessel seem greatly to aggravate both the irritation and the centripetal tendency to atrophy. In short, it is plain that such lesion of a ganglion may be the whole and sufficient cause of a neuralgia of the most desperate and incurable kind. It is another matter when we are asked to believe that the mere varying pressure of intestines, in different states of fullness, or plexuses of pelvic veins liable to temporary congestions, can so affect the sciatic nerves as to set up neuralgia. Considering the extreme frequency of cases in which such momenta must be partially coming into operation, especially in women—a frequency altogether out of proportion to that of sciatica—I cannot admit the probability that this influence is more than an occasional and very secondary factor, and that only in cases where the disposition to neuralgia is uncommonly strong.
A sufficiently complete explanation of my theory as to the pathology and etiology of neuralgia has now been given, although the subject might be elaborated at far greater length; and I hope it will be apparent to the reader that the view now advocated is at once important, and also vouched for by strong evidence. I claim for it that the whole argument shall be taken together, for it is a case of cumulative proof; every link must be weighed and tested, before the remarkable strength of the chain can be felt. And it may fairly be said that, if the proof of a definite kind of material change in a definite organ, as the essential factor in neuralgia, has been established upon reasonable grounds, an important step has been taken toward removing a serious opprobrium and difficulty in practical medicine. Although the true neuralgias are not among the most frequent of human diseases, they form a class of enormous practical importance, for they are sufficiently common to be sure to occur in considerable numbers in the practice of every medical man, and, both from the suffering which they inflict, and the rebelliousness which they often show to treatment, they are among the gravest sources of anxiety which the practitioner is likely to encounter. There are probably few disorders which so often occasion mortification and loss of professional credit to the physician. The helplessness which men, who do not enjoy special opportunities of seeing those diseases with frequency, so often show in dealing with them, is largely caused by the extreme timidity and vagueness with which the standard treatises on medicine deal with the question of their pathology; and a very unfair advantage has thus been given to the specialists, who, by the mere force of opportunity, and continual blind "pegging away" in an entirely empiric manner, have acquired a certain rude skill in the treatment of these maladies which enables them to outshine practitioners who often have far more in them of the veritable homme instruit as regards general scientific education and habits of mind. It will be evident, as a mere abstract proposition, that the enunciation of a reasonable pathology of the disease, and the sweeping away of a mass of unmeaning phrases about "mysterious functional affections" and the like, must be a distinct gain to practitioners of plain common-sense and good general knowledge, to whom neuralgia is merely one of a vast number of different diseases among which their attention and study are divided. And I hope that, in the further remarks on Diagnosis, Prognosis, and Treatment, yet to be made, the value of clear pathological ideas of disease will be brought more practically and clearly into view. [The reader will find, at the end of Part I. of this volume, a note which contains a brief discussion on the "Erschopfung" theory of Jaccoud, and the doctrines of Dr. Handfield Jones respecting inhibition, with which I thought it best not to encumber the text of the present chapter.]
CHAPTER IV.
DIAGNOSIS AND PROGNOSIS OF NEURALGIA.
Diagnosis.—This subject is much simplified and shortened, in regard to our present purpose, by the plan of the present work, which, by separately describing (in Part II.) the other disorders which resemble neuralgia, and are liable to be confounded with it, avoids the necessity for stating here the negative diagnosis of neuralgia itself. We are only concerned here to give a clear picture of the positive signs which it is necessary to verify before we can suppose disease to be neuralgia. The special modes of searching for these are interesting, and in some respects peculiar;