This is a chronic affection of the nervous system having for its most characteristic symptom a tremor, but with marked muscular rigidity and weakness. It is much more common in men than in women, in almost the reverse proportion of Graves' disease. It is usually a disease of the old, but may occur in early middle life and has been known to develop even early in the twenties. In the old days when malaria was a common diagnosis for many different conditions, paralysis agitans apparently followed malaria so often that there was thought to be some connection between the two diseases. The more we have learned of malaria the less likely this seems to be. Continuous exposure to cold for long periods and to dampness during the daily occupation for years, or repeated severe wettings, have been considered as causative elements. None of these physical factors, however, has been as directly connected with the occurrence of the affection as various emotional conditions, and the thought is suggested that even in cases of severe exposure the worry and fright and solicitude incident to the fear in an elderly person that this exposure will have serious consequences, is an important etiological element.

Psychic Factors.—Fright.—Practically all the authorities agree that mental conditions are prominent factors in the production of the disease. Serious business cares and worries and anxieties have often long preceded its development. Fright is mentioned by nearly all those who write on the subject as at least an occasion for the development of paralysis agitans if not a cause. One of my own most interesting cases occurred in the sheriff of a county of the Southwest who had earned for himself the deep enmity of an Indian by arresting him. Not long afterwards one Sunday morning when the sheriff quite unarmed came round a corner he found the Indian just in front of him wildly drunk and armed with a rifle. At once the rifle went to the Indian's shoulder, but he did not want to kill his man without having his revenge by torturing him, so he did not pull the trigger, but announced to him in vigorous though broken English that he had him now and was going to kill him. The sheriff tried to parley and for a moment the Indian permitted him to do so, apparently in order to prolong the agony. They were not more than two yards apart at the beginning, and the sheriff took his only chance and jumped and knocked the gun up. It went off just as he did so, the bullet singeing his hair. He succeeded in arresting the Indian and throwing him into jail, but the next day a tremor developed in the arm which had grasped the rifle. This spread and finally became typical of paralysis agitans. He was a man only slightly past fifty and there had been no preliminary symptoms.

Mental Control of Symptoms.—Many similar cases following fright or vehement emotion have been reported, so that it is easy to understand the feeling that the affection has a large psychic element in it, though evidently from its persistency and its continued development, there is some underlying pathological condition. The tremor may be controlled in voluntary {543} movements, while emotion exaggerates it. There is no doubt, however, that concentration of will and the definite effort to control the symptoms enables the patient to rid himself of them to a great degree for a time at least. It has been noted frequently that when a consultant physician is called the patient will be better for the day of the consultation than he had been for months before. The visits of particular friends will often arouse a sufferer to such efforts as greatly lessen his rigidity, decrease his tremor and make him capable of getting around better than before. The state of mental depression that commonly develops in these cases exaggerates the symptoms, adds neurotic and even physical conditions that develop from lack of exercise and air, and makes the patient's general state much worse than it would otherwise be.

Pathology.—Our scanty but growing knowledge of the pathology of paralysis agitans makes it clear that the disease is, in typical cases, probably due to an overgrowth of connective tissue, the neuroglia cells, in the central nervous system. Just what causes this overgrowth of connective tissue is not clear. It is an exaggeration of a normal senile process. Apparently one of the processes of age in man is a decadence of the vitality of important higher tissues with a corresponding increase of vitality in the lower or connective tissues. When Flourens declared at a meeting of the French Academy of Sciences that such an overgrowth of connective tissue was natural with advancing years, he added that this probably accounted for the slowness with which older men come to conclusions. The old members of the Academy did not accept this new-fangled doctrine with equanimity. They were inclined to think that their conservatism and deliberateness were due to greater poise of intellect.

There seems to be no doubt that at least a comparative overgrowth of connective tissue is characteristic of the brain in advancing years. In some people this occurs to a greater extent and is more precocious than in others. Just what causes are responsible for individual differences we do not know. Paralysis agitans is seen often in those who have worked hard most of their lives, but, on the other hand, may occur in those who have lived sedentary lives, and in people of all occupations. Over-indulgence in alcohol, though this is often thought to predispose to the disappearance of the parenchyma of organs and to the overgrowth of connective tissue, does not seem to have any place in the etiology of this affection. Its occurrence is a part of that mystery by which the equilibrium of different kinds of cells in the body is maintained or diminished. In a mild way paralysis agitans represents such a change in the central nervous system.

Mental Influences.—With an overgrowth of connective tissue as the pathology of the disease there would seem to be no question of any relief of its symptoms or any benefit to be derived from psychotherapy. Anyone who has much to do with cases of paralysis agitans, however, knows that they are extremely susceptible to mental influences. Whenever there is anything that interests them, any business that they feel they must do, any special event that they look forward to, they will for days at a time be so much improved in general symptoms as to be greatly encouraged themselves and make their friends feel hopeful with regard to them. When they give in to their condition, however, and make no special effort at self-control and stimulation their symptoms increase very much. Their rigidity particularly increases, their {544} tremor becomes more marked and various inconveniences associated with these two cardinal symptoms are emphasized.

Methods of Treatment.—The Vibrating Chair.—It is interesting to recall some of the forms of treatment which have been reported as beneficial in paralysis agitans, because they illustrate how much the influence of the patient's mind has over his bodily condition and how much the interest aroused in any new and particularly in any unusual form of treatment has in mitigating symptoms and how often it seems to bring about remissions in the progress of the disease. Twenty years ago Charcot suggested the use of a mechanically vibrating arm-chair. He had noticed that patients who travelled by rail seemed to have their symptoms improved for the time at least by the shaking up in the train. This treatment undoubtedly made patients much less rigid and much less tremulous. The improvement lasted sometimes for hours and sometimes for days. It was tried rather extensively and everywhere with reported good results, when first tried at least. After a time it was found that it failed to have the desired effect. Apparently whatever therapeutic value it had was due to the interest aroused in the patient's mind and the consequent effort that was made to control his muscles.

The Suspension Treatment.—When the method of treatment by suspension became popular for cases of locomotor ataxia, the idea came to try the same thing for paralysis agitans. Accordingly suspension apparatuses of many kinds were used with reported good results. Patients were suspended by the neck for some minutes and some of them got used to the treatment and could stand it for a prolonged period. The effect was always a distinct mitigation of symptoms. The rigidity particularly became much less marked, but the tremor also was lessened and besides certain secondary symptoms were bettered. Constipation was improved, partly because patients were more cheerful, ate more heartily and, above all, were willing to make some effort in order to get out regularly into the air. There was a variety in life, different from the solitary sitting at home into which these patients so often drift. Sleep was better at night and the subjective sensations of heat and cold were lessened. Patients were encouraged to think of improvement and used all their available nervous energy. In the same way when overstretching of the spinal cord by forcibly bending of the body at the hips was tried with reported success in tabes it was also applied to paralysis agitans with similar improvement of symptoms. Both methods of treatment have gone out for both these affections and evidently their observed therapeutic efficiency at first was entirely due to their effect upon the mind.

Psychic Elements and Other Remedies.—When organo-therapeutics became the fad paralysis agitans was treated also by this method. Some cases were treated with reported good results by thyroid. Later when the parathyroids attracted attention they were administered with reported good success in even very severe cases. I think that there is a report of some cases of paralysis agitans being improved by injections of diphtheria serum. In other words, anything that was given to a patient with the promise that he would be better after it and that produced a definite effect upon his mind was likely to do him temporary good. If the remedy had some special theory behind it, if there was a story of some new scientific significance for the material employed or the method of giving it, then this improvement was sure to take place. {545} In the drug treatment of the disease the same principles applied. Earlier, when nitrate of silver was the main recourse for organic nervous diseases, cases were reported improved by its administration. When the alterative properties of arsenic became a therapeutic fad this produced good effects. Atropin had for some time a reputation of relieving patient's symptoms. After a time all of them ceased to be used to any extent.

The Frenkel Method.—In recent years the application of the Frenkel directed movement method, modified somewhat from its application in tabes, has attracted attention in the therapeutics of paralysis agitans. It is interesting to note how often a mode of treatment that has been applied successfully to one of these diseases has also proved successful with the other. The two diseases are, of course, very different in etiology and pathology; but have one thing in common. The control over muscles has been lost to some degree in both cases in the progress of the disease, and a special effort of attention is required on the part of the patient in order to regulate movement. Anything that will arouse the patient to make this special effort will relieve the symptoms for a while and in tabes may bring about a lasting improvement, because the habit becomes easier after a time, though apparently this does not occur in paralysis agitans, except perhaps in the younger patients. It might very well be expected, then, that Frenkel's method in many cases would do good in paralysis agitans and it has proved to be another adjunct in the treatment of the affection. It must be used with great care not to exhaust the patient, but this is true also in tabes. The real source of its therapeutic quality seems to be the patient's interest in it and if this cannot be aroused it usually fails to do good. The success of these various mechanical methods makes it easy to understand why these patients often improve for a time under osteopathic treatment.

Psychotherapy.—It is clear, then, that the most important aid for these cases is the arousing of mental interest in some form of treatment that promises to be of benefit to them. New forms of treatment cannot always be invented and mental occupation must be secured by interest in other things. Patients suffering from paralysis agitans are prone to allow themselves to give up efforts to do things in which their interest would be aroused. They must be encouraged to do many things. Carriage riding, automobiling, train excursions, because of the effort required to resist vibration, are all helpful. They must not be allowed to drift into vacuous habits in which they make no effort for themselves. They can thus be made much more comfortable and most of their symptoms can be relieved to a marked degree. This requires constant attention and ever-renewed efforts to arouse the patient's mind and to have him make such efforts as will overcome rigidity and control the tremor to some extent; but with care an amelioration of the condition can always be brought about and can be maintained, at least to the extent of making the patient much more comfortable than would otherwise be the case.{546}