Neuralgia and the Diseases that Resemble it
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PREFACE
I believe it will not be disputed that there was considerable need for an English treatise dealing rather fully with the subject of Neuralgia, and therefore I hope that the profession will be willing to give me a hearing. The present work, moreover, does not profess to be a mere compilation of standard authorities corrected down to the present time, but puts forward a substantially new view of the subject – at least, a view that has been only briefly sketched by me in an article that appeared, three years ago, in Reynolds's "System of Medicine." My principal object, in writing this volume, was to vindicate for Neuralgia that distinct and independent position which I have long been convinced it really holds, and to prove that it is not a mere offshoot of the Gouty or Rheumatic diatheses, still less a mere chance symptom of a score of different and incongruous diseases. In order to set the diagnosis of true Neuralgia from its counterfeits in the clearest light, it seemed advisable to draw separate pictures of each of the latter (at least of as many as are of real importance) and present them separately, as a kind of gallery of spurious neuralgias, and this I have done in the second part of the volume. No one who had not tried to do it would imagine how difficult this latter kind of work is. It was necessary for the sketches to be very brief (unless my book was to become unmanageably large), and yet to be as truthfully characteristic as possible; and it was necessary also that only those diseases which so much resemble Neuralgia as practically to lead medical men astray in diagnosis, should be dealt with. The selection of the subjects, and the execution of this part, took a long time, though it only covers about fifty pages. Then, as regards Neuralgia itself, it became necessary to completely recast the chapters on "Pathology" and on "Complications," on account of some of the polite criticisms which Dr. Eulenburg directed (in his recent "Lehrbuch der Nervenkrankheiten") to my argument in the article above referred to, since it was obvious that a too brief statement of my views had caused them to be partially misunderstood by the German physician. These chapters (Part I., Chapters II. and III.) are certainly the most important portion of my book, and I would particularly direct attention to them, in order that their contents may be affirmed or corrected: the reader will at any time find that they contain a kind of investigation never before systematically carried out with regard to Neuralgia. The causes above mentioned, together with others over which I had no control, have kept back the appearance of this work so long beyond the date for which it was originally announced, that I feel I ought to apologize for an amount of delay that would seem hardly justified by the moderate size of the volume.
16 Wimpole Street, London, October 1, 1871.
INTRODUCTION.
ON PAIN IN GENERAL
Although it is, in a general way, unadvisable to introduce abstract discussions into a treatise which should be strictly practical, it is almost impossible to avoid some few general reflections on the physiological import of Pain, as a preliminary to the discussion of the maladies which form the subject of this volume. This whole group of disorders is linked together by the fact that pain is their most prominent feature; and, with regard to most of them, the relief of the pain is the one thing required of the physician. It seems, therefore, very important that we should ascertain, at least approximately, in what the immediate state consists, which consciousness interprets as pain. It is not necessary to enter at this stage into any inquiry as to the pathological causes of the phenomenon; what we know of these, and it is unfortunately too little, will be discussed in detail under the headings of the several affections which I shall have to describe.
The question before us now is this: What is that functional state of the nerves which consciousness interprets as pain? Is it, or is it not, an exaltation of the ordinary function of sensation?
The latter question is generally answered affirmatively, without much thought, by those to whom it casually occurs; but indeed there is plenty of prescriptive authority for so dealing with it. Pain has been described by some of the most distinguished writers on nervous diseases as a hyperæsthesia. Yet there is really little difficulty in convincing ourselves, if we institute a thorough inquiry into the matter, that pain is certainly not a hyperæsthesia, or excess of ordinary sensory function, but something which, if not the exact opposite of this, is very nearly so.
The leading fallacy in the common view is the confusion which is perpetually being made between function and action. Now, the function of individual nerves is very nearly a constant quantity, at least, it varies only within narrow limits; while the action of the same nerves may be almost any thing. The function of the nerve is that kind of work for which it is fit when its molecular structure is healthy; it is the series of dynamic reactions which are necessarily produced in nerve-tissue by the external influences which surround and impinge upon it in the conditions of ordinary existence. The action of nerves, under the pressure of extraordinary influences, may include all manner of vagaries which really have nothing in common with the effects of ordinary functional stimulation; which are, in fact, nothing but perturbation. No one can suppose, for instance, that the explosive disturbances of nerve-force which give rise to the convulsions of tetanus are any mere exaggerated degree of the orderly and symmetrical action by which the healthy nerve responds to the stimulus of volition ordering a given set of muscles to contract; they are something quite different in kind. And so it is with the sensory nerves. The functions of these conductors, in health, is to convey to the perceptive centres the sensations, varying only within a most limited range, which correspond to a state of well-being of the organs, and which excite only those reflex actions that are necessary to life. Thus the large surface of sensitive nerve terminals which is represented by the collective peripheral branches of the fifth cranial conveys to the medulla oblongata an impression, derived from the temperature and movement of the surrounding air, when the latter is neither too hot nor too cold, which imparts to the brain a perception of comfortable sensations, and excites in return the reflex action of breathing, which is necessary to life. But the impression produced on this same peripheral expanse of nerve-branches by prolonged exposure to cold wind may, and often does, convey to the centres sensations which are quite different and provokes reflex movements which are altogether abnormal. Pain is the product in one direction; sneezing, perhaps, in the other. It seems absurd to say that sneezing is any part of the function of those motor nerves whose action regulates the performance of expiration. And it appears to me not less absurd to say that pain is the function of the sensitive fibres of the trigeminus. But the best way, perhaps, to illustrate the looseness and incorrectness of applying the term "hyperæsthesia" (implying exalted function) to the state of sensitive nerves when suffering pain, is to examine the condition of distinctive perception in the very same parts to which the painful nerves are distributed. It will invariably be found, as we shall have occasion to see more fully proved hereafter, that, in parts which are acutely painful, a marked bluntness of the tactile perceptions can be detected. The tactile perceptions are, no doubt, conveyed by an independent set of fibres from those which convey the sense of pain.1 Yet it is surely impossible to believe the effect of the same influence, in functional power can be different – much more than it can be exactly opposite – in the two cases.
If pain be not a heightening of ordinary sensation, then we seem to be shut up to the idea that it is a perversion owing to a molecular change of some part of the machinery of sensation which frustrates function. For it is to be observed that, while the sensations conveyed by the healthy nerve are correct in the indications which they afford to the percipient brain, the indications given by pain are vague and untrustworthy, and often seriously misleading. Not to speak of the nerves of special sense, or of the fibres which convey the sensations of muscular movement, even the nerves of common sensation do carry to the internal perception, in health, a distinct impression of the well-being of the organs to which they are distributed. Mr. Bain2 has well pointed out the positive character of this feeling, which is so often incorrectly referred to as if it were a mere negation of feeling. It is a sensation of equable and diffused comfort, if I may be allowed to use the expression, which streams in from all parts of the organism; and there is no possibility of comparing it, in any scale of less or more, with the sensation of pain; for the latter commonly conveys no correct information as to the organ from which it proceeds, or appears to proceed. Especially is this the case in the neuralgias, for more commonly than not the apparent seat of the pain is widely removed from the actual seat of the mischief which causes it.
If we inquire a little further into the circumstances under which various kinds of pain occur, we gain some fresh suggestions. Among the neuralgias, those are the most acutely agonizing which occur under circumstances of impaired nutrition incident to the period of bodily decay, and strong reasons will be hereafter adduced for the belief that there is especial impairment of the nutrition of the central end of the painful nerves. To find a parallel to the severity of this kind of pains we must turn to the case of organic tumors, which, from their position, structure, and mode of growth, necessarily exercise continuous and severe pressure on the branches or the trunk of a nerve; or to the class of pains which attend severe cramp, or tonic contraction of muscles. Now, it can scarcely be doubted that in the latter instance there is an abnormally rapid and violent destruction of tissue going on; at the very least there is an extraordinarily violent and irregular manifestation of motor force. In any case the patent fact here is dynamic perturbation of a severe kind; and, in the instance of organic tumors exercising steady and continuously increasing pressure on nerves, one can scarcely doubt that a similar perturbation, less intense but more enduring, is necessarily set up. That which can be done in the way of producing severe pain by these severe affections of the peripheral portions of nerves, or of tissues lying outside them, we might a priori expect would be effected by slighter but continuous changes in the nutrition of the more important portion of the nerve itself – its central gray nucleus. One would say that a pathological process which continuously and progressively lowered the standard of nutrition here must interfere from hour to hour, certainly from day to day, with that regular and equable distribution of force which is the essence of unimpeded function.
Take, again, the case of the very severe pain which frequently attends inflammation of the pleura and of the peritoneum. Whatever theory of the causation of these pains we may adopt, it is certain that one most important element in their production and maintenance is the continual movement and friction of the affected parts. But there is little doubt that the moving muscles are involved in the inflammatory process, as Dr. Inman has correctly observed. It would seem plain that under these circumstances – an inflamed muscular structure forced to perform its ordinary contractions as well as it can – there must be powerful dynamic perturbation going on.
If perturbation of nerve-function – a disturbance quite different from mere exaltation of the normal development of nerve-force – be the essence of pain, how comes it that pains of the severest type may be produced by changes in structures which are usually described, for practical purposes, as lying outside the nervous system? We must, in the first place, remark that the externality of any bodily tissue to the nervous system is more apparent than real. Microscopic researches are constantly revealing nerve-fibres, in ever-increasing profusion, which penetrate to parts seemingly the least vitalized in the organism. But, in any case, the nerves are certainly the ultimate channel of communication between the suffering part and the sentient centre. It seems, therefore, the inevitable conclusion that a dynamic perturbation going on in the non-nervous tissue is continued along the nerves themselves: and that the severity of the pain perceived by the conscious centres is proportionate to the tumultuousness, the want of coordination, and the waste with which force is being evolved in the cramped muscle, or whatever structure it may be, in which the pain takes its source.
Not to pursue these topics further, we may sum up the considerations which have now been adduced, in the following general propositions, which will tend to simplify the examination of the various painful disorders which we are about to discuss:
1. Pain is not a true hyperæsthesia; on the contrary, it involves a lowering of true function.
2. Pain is due to a perturbation of nerve-force, originating in dynamic disturbance either within or without the nervous system.
3. The susceptibility to this perturbation is great in proportion to the physical imperfection of the nervous tissue, until this imperfection reaches to the extent of cutting off nervous communications (paralysis).
PART I.
ON NEURALGIA
CHAPTER I.
CLINICAL HISTORY
Neuralgia may be defined as a disease of the nervous system, manifesting itself by pains which, in the great majority of cases, are unilateral, and which appear to follow accurately the course of particular nerves, and ramify, sometimes into a few, sometimes into all, the terminal branches of those nerves. These pains are usually sudden in their onset, and of a darting, stabbing, boring, or burning character; they are at first unattended with any local change, or any general febrile excitement. They are always markedly intermittent, at any rate at first; the intermissions are sometimes regular, and sometimes irregular; the attacks commonly go on increasing in severity on each successive occasion. The intermissions are distinguished by complete, or almost complete, freedom from suffering, and in recent cases the patient appears to be quite well at these times; except that, for some short time after the attack, the parts through which the painful nerves ramify remain sore, and tender to the touch. In old-standing cases, however, persistent tenderness, and other signs of local mischief, are apt to be developed in the tissues around the peripheral twigs. Severe neuralgias are usually complicated with secondary affections of other nerves which are intimately connected with those that are the original seat of pain; and in this way congestions of blood vessels, hypersecretion or arrested secretion from glands, inflammation and ulceration of tissues, etc., are sometimes brought about.
The above is a general description of neuralgia which will identify the disease sufficiently for the purpose of introducing it the attention of the reader. We must now proceed to give a more accurate account of its
Clinical History and Symptoms.– These vary so greatly in different kinds of neuralgia that it will be necessary to discuss the greater part of this subject under the headings of the special varieties of the disease. There are certain common features, however, in all true neuralgias.
I. In the first place, it is universally the case that the condition of the patient, at the time of the first attack, is one of debility, either general or special. I make this assertion with confidence, notwithstanding that Valleix, and some other very able observers, have made a contrary statement. In the first place, it is certainly the case that the larger half of the total number of cases of neuralgia which come under my care are either decidedly anæmic, or else have recently undergone some exhausting illness or fatigue; and if other writers have failed to see so many neuralgic patients in whom these conditions were present, it must certainly be because they have limited the application of the term "neuralgia" within bounds which are too narrow to be justified by any logical argument; as will, indeed, be shown at a later stage. On the other hand, although a considerable number of neuralgic patients have an externally healthy appearance, as indicated by a ruddy complexion and a fair amount of muscular development, it cannot be admitted that these appearances exclude the possibility of debility, either structional or functional, of the nervous system. The commonest experience might teach us that, so far from the nervous system being invariably developed with a corresponding completeness and maintained with a corresponding vigor to those which distinguish the muscular system and the organs of vegetative life, there is often a very striking contrast between these in the same individual. What physician is there who has not seen epileptic patients, in whom mental habitude, a low cranial development, imperfect cutaneous sensibility, and other obvious marks of deficient innervation, were marked and striking features at, or even before, the first occurrence of convulsive symptoms, while the body was robust, the face well colored, and the muscular power up to or beyond the average? Now, it will invariably be found, on carefully sifting the history of apparently robust neuralgic patients, that they, too, have given previous indications of weakness of the nervous system: thus, women, who, after a severe confinement attended with great loss of blood, are attached with clavus hystericus or with migraine; will inform us that whenever, in earlier life, they suffered from headache, the pain was on the same side as that now affected, and chiefly or altogether confined to the site of the present neuralgia. In a considerable number of cases, also, in which I have been able to observe accurately the events which preceded an attack of neuralgia, it has been found that the skin supplied by the nerves about to become painful was anæsthesic to a remarkable degree; and it is very often the case that a more moderate amount of blunted sensation was perceptible in these parts during the intervals between attacks of pain. A somewhat delusive appearance of general nervous vigor is often conveyed to the observer of neuralgic patients, by reason of the intellectual and emotional characteristics of the latter. Both ideation and emotion are, indeed, very often quick and active in the victims of neuralgia, who in this respect differ strikingly from the majority of epileptics. But this mobility of the higher centres of the nervous system is itself no sign of general nervous strength; which last can never be possessed except by those in whom a certain balance of the various nervous functions is maintained. Much more will be said on this topic when we come to discuss the etiology of neuralgia. Meantime I may content myself with repeating the fact which is indubitably taught by careful observation – that neuralgics are invariably marked by some original weakness of the nervous system; though in some cases this defect is confined strictly to that part of the sensory system which ultimately becomes the seat of neuralgic pain.
Another circumstance is common to all neuralgias of superficial nerves; and, as a large majority of all neuralgias are superficial in situation, this is, for practical purposes, a general characteristic of the disease. I refer to the gradual formation of tender spots at various points where the affected nerves pass from a deeper to a more superficial level, and particularly where they emerge from bony canals, or pierce fibrous fasciæ. So general is this characteristic of inveterate neuralgias, that Valleix founded his diagnosis of the genuine neuralgias on the presence of these painful points. Herein he appears to me to be decidedly in error. I have watched a great many cases (of all sorts of varieties as to the situation of the pain), and I have uniformly observed that in the early stages firm pressure may be made on the painful nerve without any aggravation of the pain; indeed, very often with the effect of assuaging it. The formation of tender spots is a subsequent affair: they develop in those situations which have been the foci, or severest points, of the neuralgic pain. There is however, a point which, though not always, nor often, the seat of spontaneous pain, is nevertheless very generally tender. Trousseau, who criticises unfavorably the statement of Valleix as to the situation of the points douloureux, insists that this tender spot, which is over the spinous processes of the vertebræ corresponding to the origin of the painful nerve, and which he calls the points apophysaire, is more universally present than any of those pointed out by Valleix. I shall hereafter endeavor to show that these spinal points are by no means characteristic of neuralgia; they are present in a variety of affections which were ably described, under the heading of "Spinal Irritation," many years ago, by the brothers Griffin. ["Observations on the Functional Affections of the Spinal Cord," by William and Daniel Griffin. London, 1834] and they are also present with misleading frequency in cases of mere myalgia, such as I shall have to describe at a later stage.
Another characteristic of neuralgic patients in general is, I believe, a certain mobility of the vaso-motor nervous system and of the cardiac motor nerves; but I insist less on this than on the above-named features, because a more extended experience is necessary to establish the fact with certainty. Within my own experience it has always seemed to be the case that persons who are liable to neuralgia are specially prone to sudden changes of vascular tension, under emotional and other influences which operate strongly on the nervous system. The observation of this fact has been made accidentally, without any previous bias on my part, in the course of a large number of experiments made upon individuals free from manifest disease at the time, with Marey's sphygmograph.
Neuralgic attacks are always intermittent, or at the least remittent, in every stage of the disease.
The manner in which neuralgic pain commences is characteristic and important. There is always a degree of suddenness in its outset. When produced by a violent shock, it may, and often does, spring into full development and severity at once, of which, perhaps, the most striking example is the sudden and violent neuralgic pain of the eyebrow which some persons experience from swallowing a lump of undissolved ice. Usually, however, the first warning is a sudden, not very severe, and altogether transient dart of pain. The patient has probably been suffering from some degree of general fatigue and malaise, and the skin of the affected part has been somewhat numb, when a sudden slight stitch of pain darts into the nerve at some point which corresponds to one of the foci hereafter to be particularized. It ceases immediately, but in a few seconds or minutes returns; and these darts of pain recur more and more frequently, till at last they blend themselves together in such a manner that the patient suffers continuous and violent pain for a minute or so, then experiences a short intermission, and then the pain returns again, and so on. These intermittent spasms of pain go on recurring for one or several hours; then the intermissions become longer, the pain slighter, and at last the attack wears itself out. Such is generally the history of first attacks, especially in subjects who are not past the middle age, nor particularly debilitated from any special cause.
A point of interest in connection with the natural history of the neuralgic access is the condition of the circulation. The commencement of pain is generally preceded by paleness of skin and sensations of chilliness. At the commencement of the painful paroxysm, sphygmographic observation shows that the arterial tension is much increased, owing, in all probability, to spasm of the small vessels. This condition is gradually replaced by an opposite state, the pulse becoming large, soft, and bounding, though very unresisting, and giving a sphygmographic trace which exhibits marked dicrotism. Simultaneously with this the skin becomes warmer, sometimes even uncomfortably warm, and there is frequently considerable flushing of the face.