Lissauer52 has recently determined the existence of a degeneration of certain fine nerve-fibres, apparently derived from the outermost of the radicles into which the posterior nerve-roots divide on entry. They are situated on that border of the apex of the posterior horn which is in contact with the lateral column, and were found degenerated in all cases except such as were in the initial period. No symptomatic relation has been claimed for this lesion.
52 Neurologisches Centralblatt, 1885, No. 11.
One of the most important questions which have grown out of the pathological studies of tabes is the relationship between the lesions and the not infrequently observed restoration of functions which had been more or less seriously impaired in an earlier period of the disease. Even those symptoms which ordinarily comprise the continuous and essential clinical background of tabes may exhibit remarkable changes in this direction. I have two well-established observations—one of tabes of eight years' standing, the other of more recent date—in which that symptom which, once established, is the most constant, the reflex iridoplegia, disappeared, to reappear in two months in one case where it had been associated with myosis, and to reappear in eight months in the other, repeating this oscillation the following year. I have now under observation a tabic patient in the sixth year of his illness who two years ago had a return of both knee-phenomena to a nearly normal extent, to lose them in two months, and to regain the reflex on the left side four months ago, retaining it up to the present. These three cases were of syphilitic subjects. In a fourth advanced non-syphilitic tabic patient, whose ataxia had reached a maximal degree, I found a return of both knee-phenomena for three days after its absence had been established by medical examiners for over a year, and had probably been a feature for a much longer period. Hammond the younger and Eulenburg have reported similar cases. Nothing is more surprising to those unfamiliar with the progress of this disease than to find gross ataxia or the electrical pains and anæsthesia to disappear or nearly so; and the alleged success of more than one remedial measure is based on the fallacious attributing to the remedy what was really due to the natural remittence of the disease-process or of its manifestations. The financial success of quacks and the temporary but rapidly evanescent popularity of static electricity, Wilsonia belts, and like contrivances are owing to the hopefulness inspired in the credulous patient by the mere coincidence of spontaneous improvement and the administration of a new remedy, supplemented, it may be, by the influence of mind on body in his sanguine condition. It is to be assumed that the influences which are at work in provoking the trophic and visceral episodes of tabes are of an impalpable character, and that all theorizing regarding the reason of their preponderance in one and their absence in another case are as premature as would be any speculation regarding their rapid development and subsidence in the history of one and the same case. But we have better grounds for explaining the remissions of the ataxia and anæsthesia.
It is only in the most advanced stages of tabes that the destruction of the axis-cylinder becomes absolute or nearly so. Contrary to the opinion of Leyden,53 who held that the tabic sclerosis differs from disseminated sclerosis in the fact that the axis-cylinder does not survive the myelin disappearance, it is now generally admitted that a certain number of exposed or practically denuded axis-cylinders may be preserved in the sclerotic fields.54 It is on the theory that these delicate channels may be oppressed at one time, perhaps by inflammatory or congestive pressure, and relieved at another by its subsidence, that we may assume them to be the channels through which the now limited, now liberated, functions are mediated. It is also reasonable to suppose that vicarious action may supplement the impaired function, and to some extent overcome the disturbing factors. This is illustrated by the controlling influence of the visual function—yea, even of the unconscious and ineffectual co-operation of completely amaurotic eyes—in neutralizing both locomotor and static ataxia. One patient who was well advanced in the initial period of tabes, and who had been encouraged to consider the medical opinion to that effect as the result of an exaggerated refinement of diagnosis, made repeated tests of the Romberg symptom in his own case, and deluded himself into the belief that the physician was mistaken because he succeeded in practically overcoming it with an effort that too plainly told its own story; but still he overcame it. Certain peripheral influences have the power of stimulating the dormant activity of potentially vicarious tracts, and perhaps also the blunted activity of those whose function is impaired. The outside temperature, certain barometric conditions, all may exert an influence in this direction for good or evil.
53 Op. cit., p. 328, vol. ii.
54 Babinski (Neurologisches Centralblatt, 1885, p. 324) notes this feature, and, consistently with the findings of most modern observers, discovers much more resemblance to disseminated sclerosis than to the systemic sclerosis with which Strümpell and Westphal (in part) incline to classify tabes. Similar objections to the system-disease theory are advanced by Zacher (Archiv für Psychiatrie, xv. p. 340). I may not pass over in silence the fact that Babinski considers his observations to militate also against regarding any phase of the tabic sclerosis as a secondary process. But while it may fairly be asked that a sclerosis to be regarded as systemic must be shown to be total, this is not necessary for a secondary process, unless the primary involvement be total also; and that is not the case in tabes.
ETIOLOGY.—Authorities are now agreed that no single cause can be regarded as the sole responsible factor in all cases of tabes, and that a number of etiological influences are combined in the provocation of this disease in most instances. When the distinctiveness of the affection was first recognized it was customary to attribute it to sexual excesses, and the unfortunate sufferer had frequently to bear the implied reproach of having brought his misery on himself, in addition to the hopeless prospect which those who followed Romberg and other authorities of the day held out to him.55
55 This opinion survives in a large portion of the German laity and in French novels. About the time that the poet Heine was dying from an organic spinal affection two other prominent literary characters of Paris were affected with tabes. It so happened that all three were popularly regarded as libidinous, and one of their leading contemporaries, whose name escapes me, took occasion to issue a manifesto addressed to the jeunesse dorée which closed with the apostrophe, “Gardons à nos moelles.”
Heredity plays a very slight part in the etiology of tabes. Writers of ten and fifteen years ago attributed a greater importance to it than is now done. But this was due to the incorporation with tabes of the so-called family form of locomotor ataxia—a disease which is now regarded as a distinct affection.56
56 There is but one record of direct heredity (the father and son being affected nearly at the same time), to my knowledge. It was observed at the Berlin Hospital by Remak (Berliner klinische Wochenschrift, 1885, No. 7). Both father and son were syphilitic.