It has surprised me, somewhat, that while M. Mauriac has seen so many reflex neuralgias set up by orchi-epididymitis, he does not appear to have noticed cases of trigeminal neuralgia from this source; because, in the very analogous instance of the peripheral irritation produced by excessive masturbation, we undoubtedly do frequently get a development of the tendency to migraine, and also to other forms of neuralgia of the fifth: moreover the effect of such local irritation can be occasionally traced with much distinctness in the trigemini, by a tendency to certain forms of eye-disease without positive neuralgia. This was remarkably exemplified in a case which was under my care some years ago, and in which both eyes were greatly damaged by vaso-motor and trophic changes; partial insanity also supervened with hallucinations of sight and hearing.
We come now to one of the most powerful sources of peripheral irritation tending to set up neuralgia; viz., functional abuse of the eye. This is one of the very few peripheral influences which occasionally we see producing neuralgia unaided by hereditary predisposition, or any other observable cause whatever, and in a far larger number producing it with the sole aid of more or less defective general nutrition. The latter occurrence is well exemplified by a case which Mr. Carter sent me the other day, and which also illustrates (second attack) the effect of the superaddition of syphilitic taint:
Matilda W——, aged thirty-three, married, and has three very healthy children. Comes of a remarkably healthy family, of which she told me the entire history for three generations, with unusual intelligence and clearness. No neuroses, properly so-called, in any of her relatives during all this time. She herself was a very strong and hearty girl until the age of seventeen; between this date and her marriage, three years later, she was obliged to work tremendously hard at fine sewing, by which means she gained a very scanty livelihood. After a comparatively short period of this work she began to suffer from typical attacks of migraine, very severe, and recurring every three or four weeks, but in no particular connection with the menstrual function, which was normal. On her marrying and ceasing to do needle-work, the migraine entirely disappeared, and she retained perfect health till the commencement of 1871. At this time she had suckled a very hearty baby for ten months, and was not able to furnish such good living as usual. She was attacked early in January, with violent neuralgia affecting all three branches of the right fifth, and she the more readily applied for advice because she soon found that the neuralgia was becoming complicated with dimness of vision in the eye of the affected side, "as if she was going to have a cast." Was quite unconscious of ever having had syphilis. The medical man encouraged to believe that the whole malady was nervous, and would soon disappear under appropriate remedies, and gave her quinine, under which treatment she declares that she was rapidly improving, both as to pain and vision, but that her resources came to an end, and she could no longer pay for the medicine. She then neglected herself, and rapidly got worse in all regards, till at last she was compelled to apply to the South London Ophthalmic Hospital, whence Mr. Carter sent her to me, on the 6th of April. At this time the paroxysms were excessively violent and frequent, though brief. On examination, tender points were found at the supra-orbital notch, at the infra-orbital foramen; in front of the ear; in the temporal region; in the parietal region, and the inferior dental region. There was strongly marked anæsthesia of the skin of the right half of the face, of the gums, and of the side of the tongue. The teeth were absolutely perfect: not one spot of caries could be seen. Taste was completely destroyed in left half of anterior part of the tongue. Smell was totally lost on both sides, and had been so, the woman declared, from a very early period in the illness. The right eye showed complete paralysis of the levator palpebræ and of the external rectus; nearly complete paralysis of the superior and inferior rectus, rather less marked paralysis of the internal rectus. Pupil normal, conjunctiva moderately congested, lachrymation profuse, photophobia partial. The functions of the retina were perfect. Accommodation was affected in the following degree and manner. The vision of the affected eye was perfect at long distances, very imperfect at short distances. With both eyes open she saw every thing double, but could still count all the bricks in a whitewashed wall at sixteen feet distant. There was no secondary disturbance of the stomach whatever. On the first visit she assuredly had no visible signs, in skin or throat, of syphilis; the perfect health of her children, and absence of abortions, made syphilis the less probable. But on her second visit she complained of sore throat, and a week later a palpably specific sore appeared on the soft palate. She declared, with apparent sincerity, that it was the first symptom of the kind she had ever had. The neuralgia rapidly disappeared under thirty grains of iodide of potassium daily. The lesions of taste and smell disappeared exactly pari passua with the trigeminal pains. The ocular paralysis threaten to be much slower in departing. I think we must believe that this woman contracted syphilis after the birth of her last child. It is at any rate certain that the migraine of her youth was perfectly unconnected with syphilis, being as unlike the pains evoked by the latter as it is possible for two kinds of pain to be. In all probability she was infected during her last lactation.
Last among the peripheral influences of sufficient importance to be specially mentioned as effective factors in the production of neuralgia, must be mentioned caries of the teeth, and the comparatively rare accident of the mal-position or abnormal growth of a "wisdom-tooth." It is an undoubted fact that these things may cause neuralgia even of a very serious type, and attended with extensive complications; as in Mr. Salter's cases, already mentioned, of reflex cervico-brachial neuralgia from carious teeth. Looking to the extreme frequency of caries, however, as compared with the rarity of true neuralgia (not mere toothache) as a consequence of it, it is impossible not to suppose that the share of the carious teeth in the production of such neuralgia must be very small, compared with that of other influences.
5. The next influence which we shall mention as undoubtedly very effective in assisting the production of neuralgia in certain cases is that of anæmia and mal-nutrition generally; but it is not necessary to dwell on this at any length. The fact is notorious that severe loss of blood is always followed by headache; and if there be the least predisposition to neuralgia, this headache will very commonly take the form of the severest clavus. And, in like manner, chronic states of anæmia and of mal-nutrition undoubtedly aggravate every existing neuralgia, and bring out lurking tendencies to the disease. But I do not believe that anæmia, or starvation pure and simple, ever generates true neuralgia by its sole influence.
6. The question how far, and in what way, the neuralgic tendency is helped by certain constitutional diatheses, such as rheumatism and gout, and by certain toxæmiæ, such as malaria, alcoholism, lead-poisoning, etc., is a very much more difficult one than might be supposed from the off-hand manner in which many writers speak of the "rheumatic," the "gouty," or the "alcoholic" forms of "neuralgia." We may, however, simplify it a good deal. In the first place, it seems obvious to me that the only manner in which alcohol helps the production of true neuralgia is by its tendency, after long abuse, to produce degeneration of the nervous centres: it will therefore be considered, shortly, under another division of the present subject. Lead-poisoning, again, only produces so highly special a form of neuralgia (if colic be neuralgia at all) that it need not detain us here. The influence of malaria is, for the most part, an utter mystery to us, but by so much as we can see it appears plain that one of the most important features in the disease is a powerful disturbance of the spinal vaso-motor centres. But the most interesting consideration that we have to deal with is the question of the supposed relations of the rheumatic and the gouty diatheses, and the syphilitic dyscrasia, to the neuralgic tendency. On this point I am obliged to disagree in toto with the popular view that assigns these diatheses among the most frequent predisposing causes of neuralgia.
To take the case of rheumatism first, I am willing to allow that there are a number of facts which superficially appear to countenance the idea of a close connection of this disease with neuralgia. But of these facts a considerable proportion consist only of examples of inflammation of the nerve-sheath, with a certain amount of effusion within and around it, occurring in persons who have never shown any symptoms which warrant the assumption of a general rheumatic diathesis; and these local phenomena really differ in nothing from many trophic and vaso-motor changes which have been already described as plainly secondary to ordinary neuralgia in which there could be no pretence of a rheumatic pathology except on the slender foundation of a suspicion that the affection was immediately excited by the influence of cold, which is really no argument at all. Such patients will be found to have exhibited, not special rheumatic, but special neuralgic tendencies in their past history. On the other hand, there undoubtedly are a certain number of patients who, having previously given signs of a tendency to generalized rheumatic inflammation of fibrous membranes, are, on some particular occasion, attacked with similar inflammation extending over a more or less considerable tract (not a small limited spot) of a nerve sheath. But so far from agreeing with those who think that this is a frequent case, my experience teaches me that it is quite exceptional; nor do I believe that the common opinion could ever have arisen had it not been for the rage that exists for connecting every disease with a special diathesis which the profession flatters itself that it understands. Few persons have taken more pains than myself to ascertain the frequency with which neuralgic patients show a history of previous rheumatism, whether in the so-called "fibrous," or in the synovial form; but it is remarkable how seldom I have found this to be the case—a result which surprised me, because it happened that I, a neuralgic subject, had suffered in youth from regular acute rheumatism, and had fancied that I should discover a close connection between rheumatism and neuralgia. Eulenburg states that neuralgia caused by cold more frequently attacks the sciatic nerve than any other, and thinks that the tendency to sciatica is characteristic of the relations of rheumatism to sensory nerves. For my own part, I see no reason to call in the rheumatic diathesis as a deus ex machina to explain the frequency with which sciatica follows comparatively trifling peripheral impressions like that of cold. The true reason I believe to be, that what would have been a slight and trivial neuralgia elsewhere, becomes a serious affection in the instance of the sciatic nerve, by reason of the strong muscular pressure end dragging which are always going on in the thigh in locomotion. I shall return to this subject when speaking of Treatment.
As regards the relations, of gout to neuralgia, I can hardly express my own view better than by quoting the words of Eulenburg:[17] "Much more doubtful is the influence of gout, which in rare cases, perhaps, produces neuralgia directly, by means of neuritis, or by the deposit of tophus-like calcareous concretions in the nerve-trunks. Gout has been reckoned as a great influence among the causes of superficial neuralgias (sciatica), and also of visceral neuralgia (angina pectoris, etc.,) but this influence is more probably only an indirect one, operating through circulation changes which are often produced by chronic liver-diseases or by diseases of the heart and vessels, (e. g. Valvular diseases and narrowing of the coronary arteries in angina)." To which I will add this argument against any close connection of gout with neuralgia, that it is exceedingly seldom that colchicum effects any decided good, a fact which is as unlike the relations of colchicum to true gout as any thing could be. For, whatever may be thought of the advantages or disadvantages, on the whole, of employing colchicum against gout, at least no one with any experience will deny that in the immense majority of cases of true gouty pain, it gives rapid relief to the acute suffering. I doubt if it ever[18] acts in that way in real neuralgia, though I have occasionally seen it apparently useful in a more limited way, as will be said hereafter.
As regards the relation of the syphilitic dyscrasia to neuralgia, I agree in general with Eulenburg. "Syphilis," he says, "may be the direct cause of neuralgia, either by the development of specific gummata in the nerve-trunks or in the centres, or by arousing chronic irritative processes in the nerve sheaths, the membranes of the brain and spinal cord, or, especially, in the bones and periosteum (syphilitic osteitis and periostitis)." The case of periostitis, however, is a doubtful one: it may be questioned whether this affection (which will be among the diseases discussed in Part II. of this work) ever give rise to true neuralgia. Persons who are, by inheritance, highly predisposed to neuralgia, may from the mere general lowering of their health produced by constitutional syphilis, become truly neuralgic simultaneously with, or subsequently to, the appearance of painful nodes on their bones. And as regards the whole relations of syphilis to neuralgia, I must, from my experience, conclude that the former is, after all, but rarely concerned in the production of the latter. Syphilis has a strong specialty for producing limited motor paralyses, but a much weaker one for producing limited affections of the sensory system.
7. We now come to the discussion of a group of momenta whose influence in the production of neuralgia is at once very powerful, and of the highest significance as regards the general pathology of the disease. These are the degenerative changes of the arterial and capillary systems which are a part of the normal phenomena of old age, but may occur at earlier periods of life, in consequence either of certain constitutional diseases, especially gout, or of special toxic influences on nutrition, of which persistent alcoholic excess is very far the most important.