I have under observation a patient who has been compelled to use the catheter daily for years, who has gradual disappearance of the knee-jerk and reflex iridoplegia, but who has presented no other evidence of tabes during the year and a half he has been watched. Among the exact signs of tabes, reflex iridoplegia and abolition of the knee-jerk are probably the earliest to appear. It may be assumed with safety that in ninety-nine out of a hundred cases both the inability of the pupil to respond to light and the absence of the knee-jerk will be found long before ataxia is developed. Cases are recorded where no other positive signs were found, and no other signs of the disease developed for a number of years,5 and others where disappearance of the knee-jerk was the very first indication.
5 Westphal, also Tuczek, Archiv für Psychiatrie, xiii. p. 144.
The opinion of observers as to the frequency of double vision as an early symptom of tabes is far from being unanimous. The majority of writers speak of it as rare, but it is probable that this usually transient symptom is forgotten by the patient, or because of its apparent triviality escapes notice. The patient while looking at an object sees a double image of the latter. This may last for a few seconds, minutes, or hours, and rarely for a day or week.6 A distinct history of this symptom was given by 58 out of 81 patients in whom I recorded the oculo-motor signs. By far the most important of the exact prodromal signs of tabes are two symptoms—one involving a special faculty of co-ordination, the other the reflex movements of the pupil. One or both of these must be present to justify the diagnosis of incipient tabes.7 The disturbance of co-ordination consists in an inability of the patient to stand steadily when his eyes are closed. The majority of healthy persons when tested in this way may show a little swaying in the beginning, but eventually they stand as steadily as they do with open eyes, and there is no subjective feeling of uncertainty as to falling. But the tabic patient exhibits oscillations, and makes efforts to overcome them which, instead of neutralizing, usually aggravate them and betray the great disturbance of his equilibrium. It is not as if he swayed merely because he is uncertain of his upright position, but as if some perverted force were active in throwing him out of it. It is found to be a pronounced feature even in cases where the patient with open eyes is able to walk nearly as well as normal persons, and experiences no trouble in performing intricate evolutions, such as dancing, walking a line, or even walking in the dark—faculties which the patient is destined to lose as his disease progresses.8
6 It has been asserted that the severer and more persistent diplopias are found with tabes dependent on syphilis.
7 Not even the absence of the knee-jerk ranks as high as these two signs. Aside from the fact that this is a negative symptom, it is not even a constant feature in advanced tabes.
8 It does not seem as if the disturbance of static equilibrium were due merely to the removal of the guide afforded by the eyes, for it is noted not alone in patients who are able to carry out the average amount of locomotion in the dark, but also in those who have complete amaurosis. Leyden (loc. cit., p. 334) and Westphal (Archiv für Psychiatrie, xv. p. 733) describe such cases. The act of shutting the eyes alone, whether through a psychical or some occult automatic influence, seems to be the main factor.
In most cases of early tabes it is found that the pupil does not respond to light; it may be contracted or dilated, but it does not become wider in the dark nor narrower under the influence of light. At the same time, it does contract under the influence of the accommodative as well as the converging efforts controlled by the third pair, and in these respects acts like the normal pupil. It is paralyzed only in one sense—namely, in regard to the reflex to light; just as the muscles which extend the leg upon the thigh may be as powerful as in health, but fail to contract in response to the reflex stimulus applied when the ligamentum patellæ is struck. For this reason it is termed reflex iridoplegia.9 It is, when once established, the most permanent and unvarying evidence of the disease, and is of great differential diagnostic value, because it is found in comparatively few other conditions.
9 It is also known as the Argyll-Robertson pupil. Most of the important symptoms of tabes are known by the names of their discoverers and interpreters. Thus, the swaying with the eyes closed is the Romberg or Brach-Romberg symptom; the absence of the knee-phenomenon, Westphal's or the Westphal-Erb symptom; and the arthropathies are collectively spoken of as Charcot's joint disease.
In a number of cases ptosis of one or both eyelids is noted at an early stage of the disease. It is usually temporary, and coincides as to time with the diplopia, if present.
Patients presenting some or all of the subjective and objective manifestations of tabes mentioned may continue in a condition of otherwise comparative health, enabling them to attend to their vocation for from one to twenty years, and it is not improbable that the pre-ataxic period may extend over nearly a lifetime. In a less fortunate minority of cases some of the most distressing evidences usually marking the last stages of the disease are found developed at the onset. Thus, cases are known where optic nerve-atrophy preceded the true tabic period by ten or more years; others in which trophic disturbances, manifested in spontaneous fractures of bones10 or violent gastric crises, or even mental disturbance, inaugurated tabes dorsalis, instead of closing or accompanying the last chapter of its history, which is the rule.