Multiple Neuritis, Multiple Degenerative Neuritis, Polyneuritis.
Cases of this important form of neuritis have been observed and recorded since 1864, but the resemblance of its symptoms to those of certain diseases of the central nervous system (poliomyelitis, Landry's paralysis, etc.) has prevented its general recognition, and it is only within the last few years that its distinctive pathological lesions have been demonstrated and its diagnosis made with considerable certainty. We can hardly overrate the importance of this in view of the great difference in gravity of prognosis between it and other diseases with which it may be confounded.
Multiple neuritis consists in a simultaneous or more or less rapidly succeeding inflammation of several or many usually bilaterally situated nerves, with a greatly preponderating, almost exclusive, lesion of the motor fibres. Commonly the disease attacks the lower extremities and progresses upward, although occasionally it has been seen to begin in the arms. It does not confine itself to the nerves of the extremities and trunk, but often involves the phrenics, causing paralysis of the diaphragm, and frequently invades one or more of the cranial nerves, notably the vagus, thus giving rise to the rapid heart-beat so often seen in the disease. In the cases of multiple neuritis observed the muscles of deglutition have never been paralyzed. The sphincter ani and bladder have likewise escaped. All degrees of acuteness are observed in the course it runs, from the cases terminating rapidly in death to those in which the disease extends over months, slowly involving nerve after nerve, until nearly all of the muscles of the body are paralyzed, when death may result or a more or less complete recovery take place. The invasion of the disease is in most cases sudden, even when its subsequent course is chronic, and is often marked by decided constitutional disturbance, as rigors, fever, delirium, albuminuria, etc. Disturbances of sensation are prominent among the initial symptoms, and are of great importance for the diagnosis of the disease. Severe, spontaneous, paroxysmal pain of a shooting, tearing character has ushered in most of the cases on record, remitting, however, during their progress. Pain is not always present, nevertheless, and cases not infrequently occur which run a painless course. In some cases which have come under the writer's notice spontaneous pain did not occur until some days after the disease was fully declared by other symptoms. More constantly present, and more characteristic of multiple neuritis, are the disturbances of sensation which show themselves in subjective feelings of numbness, tingling, pins and needles, coldness, burning, and other paræsthesiæ, which appear at its outset and continue to be present more or less during its course. Anæsthesia, not of a high degree nor at all coextensive with the paralysis of the muscles—sometimes, indeed, confined to very circumscribed areas—may be said to exist always in multiple neuritis—a fact of great diagnostic value. Hyperæsthesia of the skin is frequently seen. Hyperalgesia and analgesia are sometimes observed. Hyperæsthesia of the muscles is a very marked symptom in almost every case, and shows itself not only upon direct pressure being made, but also in the pain elicited by passive movements of the parts affected. Pressure upon nerve-trunks does not cause pain as invariably as might have been expected from the location of the disease. Delayed sensation has been frequently observed.
Paresis of muscles, often commencing suddenly, is early seen in multiple neuritis, and increases until there is more or less complete paralysis, the most important feature of the disease. The paralyzed muscles present the flabby condition characteristic of muscles deprived of the tonic influence of the spinal cord. Atrophy, which is not commensurate, however, with the paralysis, soon begins, and may go on to an extreme degree. As the paralysis develops the tendon reflexes are lost, and there may be diminution or loss of the skin reflexes also. The paralyzed muscles lose their faradic contractility, and exhibit diminution of electric excitability to the galvanic current, and, finally, the various forms of degenerative reaction. It is remarkable that neither the impairment of sensation nor the paralysis is, as a rule, strictly confined to the areas of distribution of particular nerves, but is diffused over regions of the body. Thus in the limbs the motor and sensory symptoms are most marked at their extremities, gradually diminishing toward the trunk. In some cases multiple neuritis appears to have occasioned the inco-ordinate movements of locomotor ataxy. In the progress of the disease a rigidity and contracted condition of muscles may be developed, occasioning a fixed flexion of some of the joints. Profuse sweating, œdema of the hands and feet, trophic changes in the skin, mark at times the implication of trophic and vaso-motor nerves. Bed-sores do not occur.
The pathological changes in pure cases of multiple neuritis are found in the nerve-trunks, mainly toward their peripheral terminations, and in their muscular branches, the evidences of disease diminishing toward the larger trunks, the nerve-roots being unaffected and the spinal cord showing no lesions. Sometimes the affected nerves present, even to the naked eye, unmistakable proof of acute inflammation. They are reddened by hyperæmia, swollen by exudation, and small extravasations of blood may be seen among their fibres. The microscope shows congestion of the blood-vessels, exudation of the white corpuscles, even to the formation of pus, alteration of the endo- and perineurium; in short, all the evidence of an interstitial inflammation, the nerve-fibres being comparatively little altered, and suffering, as it were, at second hand. In most of the cases, however, the nerves macroscopically present little or nothing giving indication of disease. The microscopic changes, however, are extensive, and pertain almost exclusively to the nerve-fibres themselves. These are altered and degenerated, giving an appearance almost precisely the same as already described in treating of the changes occurring in nerves separated by injury from the centres—Wallerian degeneration.8 There is no hyperæmia, thickening, or change in the endoneurium. So great are these differences in the microscopic appearance of the nerves in different cases of multiple neuritis that objection has been raised to classing the two varieties together, and it has been argued that we cannot with right designate the cases in which hyperæmia and other evidence of a general inflammation are absent as neuritis. It has been, however, argued—apparently, to the writer, with better reason—that the same morbid influence which at one time affects the blood-vessels, causing their congestion and the passage through their walls of the white corpuscles and the exudation of inflammation, may at another time, by a direct and isolated influence upon the nerve-fibres, cause their degeneration; in other words, that there may be a parenchymatous neuritis, which shall affect only the nerve-fibres. The vastly disproportionate implication of the motor fibres would point to the fact of a selective infection in multiple neuritis of certain fibres, as there is a selective infection in poliomyelitis of the motor cells of the anterior horns of the spinal gray matter.
8 Gombault's observations (Arch. de Névrologie, 1880) would seem to show that there is a difference in the lesion of the fibres in neuritis from that in simple Wallerian degeneration, inasmuch as that in the former the first alteration is seen about the nodes of Ranvier, and occurs at points separated from each other by healthy fibre, and also in the more tardy destruction of the axis-cylinder.
ETIOLOGY.—Much in the symptomatology of multiple neuritis, especially of its invasion, strongly urges us to the conclusion that it is a constitutional disease caused by an unknown morbid influence, the stress of which falls upon the nervous system. This view receives strong support from the history of the Japanese kak-ke or Indian beriberi, a disease at times epidemic in those countries, and which has the undoubted symptoms and the characteristic pathological alterations of multiple neuritis. After many acute infectious diseases neuritis of individual nerves is not uncommon, but the distinctive characteristics of multiple neuritis have, so far, been observed almost exclusively after diphtheria, to which it is not infrequently a sequel. It has been observed as the result at least occurring in intimate connection with polyarthritis, and the frequency with which it has occurred in the phthisical is remarkable. There have been not a few cases of multiple neuritis recorded as having been produced by chronic alcohol-poisoning. A well-marked case has come under the writer's observation in which the immediate cause was acute poisoning by arsenious acid, a very large amount having been taken at one dose by mistake. The poison of syphilis has been regarded as standing in a causal relation to multiple neuritis. For the rest, the exciting causes (probably acting in connection with a peculiar condition of the system) have appeared to be exposure to cold, great muscular exertion, direct mechanical injury to the nerves, as the rough jolting of a wagon, or the inflammation of a nerve which has in some unknown way extended to others.
The DIAGNOSIS of multiple neuritis in certain cases presents great difficulty, from the close resemblance of its symptoms to those of poliomyelitis. The prominent symptoms in the muscular system—viz. paralysis, atrophy, the degenerative reaction—are the same in both. It may be remarked, however, that in multiple neuritis the paralysis is more generally diffused over the muscles of the affected limbs, while in poliomyelitis it is more confined to the areas of distribution of particular nerve-branches. Pain is common to the beginning of both diseases, but it generally passes off more quickly and completely in poliomyelitis. The persistent hyperæsthesia of the muscles is wanting in poliomyelitis. But it is in the diminution and alteration of sensation that we have the surest means of distinguishing between the two affections. This symptom seldom or never fails to show itself in multiple neuritis, although its area may be circumscribed and it may be slight in degree, while it certainly makes no part of the symptomatology of poliomyelitis. It has been asserted that the implication of the cranial nerves so often seen in multiple neuritis never occurs in poliomyelitis. When we consider the intimate connection of the anterior horns of the spinal gray matter with the motor nerve-fibres, it appears highly probable that the same morbid influence may invade both simultaneously or in quick succession, thus producing a complex of symptoms rendering a diagnosis very difficult, and probably giving rise to some confusion in the recorded symptoms of multiple neuritis. From Landry's paralysis multiple neuritis is to be distinguished by the impairment of sensibility, the loss of faradic contractility, and absence of the tendon reflex; from progressive muscular atrophy, by the loss of sensibility and the much more obvious degenerative reaction.
The PROGNOSIS of multiple neuritis is in the great majority of cases not grave, so far as life is concerned, even when there is extensive paralysis. Death may occur early in the acute form of the disease or it may take place at the end of chronic cases. When the disease proves fatal, it is from paralysis of the diaphragm and the other muscles of respiration. Where the paralysis and atrophy have been great, showing profound alteration of the nerves, a long time is required for recovery, and more or less paralysis, contracture, or defective sensibility may permanently remain.