SYMPTOMS.—The course of the disease has been divided into three stages—the period of invasion, the stationary period, and the terminal period.1
1 Lectures on Diseases of the Nervous System, by J. M. Charcot.
Period of Invasion.—There are several modes of invasion, but the most frequent by far is slow in its onset. The disease comes on gradually, first showing itself as a slight tremor in the hand or fingers while the part is at rest. It is not constant, and ceases as soon as the patient's attention is called to it. There is sometimes preceding the tremor rheumatic or muscular pain in the affected arm. The tremor may first occur in the foot. Should the disease begin in the hand—and this is most common—the movements are peculiar. They may consist of a fine rhythmical tremor, or the fingers move in a methodical way over each other. Charcot speaks of the thumb and forefinger being rubbed together as if the patient were spinning wool. While this movement of the thumb and finger is going on the wrist is being flexed by jerks. During the early stages of the disease the tremor is observed only at intervals. It comes on intermittently when the patient is not thinking of it and while the limb is at rest, and ceases as soon as any voluntary muscular effort is attempted. The act of grasping the hand or taking up an object is enough to check it for the time. In a patient now under my care I have often noticed during the early stages a well-marked tremor of the right hand while it was lying in her lap, but it would at once cease when I called attention to it. As soon as the mind of the patient was diverted to some other subject the tremor would begin again.
As the disease progresses voluntary effort no longer controls the tremor, or if it does at all it is only for a few seconds, when it begins again. As the tremor increases in violence it extends to other parts of the body. At first it may have been confined to the hand; now it extends to the arm, a little later to the foot and leg on the same side. Then the other arm will be affected, and finally all of the limbs will succumb to the tremor.
Charcot speaks of decussated invasion—that is, the disease begins in the right upper extremity, for example, and next passes to the left lower extremity. This is a rare form; it is much more frequent to see the hemiplegic type, which may persist for some time, or the paraplegic type, when both legs are affected.
There is a progressive form of invasion when the tremor is not the first symptom. The patient has neuralgic or rheumatic pains in the limbs, which are afterward affected with tremor. Sometimes there is some mechanical injury of the limb, which subsequently is the seat of pain and tremor. The general health of the patient is at the same time more or less impaired. There is a sense of general weakness and lassitude; the temper is irritable, and there may be some vertigo. The features and countenance are characteristic even at the earliest periods of the disease. There is an absolute absence of expression, and the features are fixed. The face looks like a mask, and although the patient may smile or laugh, immediately after the features return to the original blank expression. Amidon showed two cases of paralysis agitans to the American Neurological Society in 1883, in which there was no tremor whatever, but all the other features of the disease were present.
After a great mental or moral shock the trembling begins suddenly, abrupt invasion, as in Case I., or the case described by Charcot, where the wife of a gendarme, seeing her husband's horse return riderless to the barracks, received a shock of great severity, which was followed on the same day by tremor. The tremor is at first confined to one limb. It may even disappear for a time, but gradually and slowly extends to the other limbs, and takes the same progressive course.
Period of Stationary Intensity.—After the disease has become fully developed the tremor is incessant. The intensity is not the same all the time. It may be augmented by cold, over-excitement, or voluntary effort, and is lessened by repose and sleep. The trembling ceases during anæsthesia.