TREMOR.
BY WHARTON SINKLER, M.D.
Tremor is a prominent symptom of many diseases of the nervous system, and is met with as an effect of certain poisons which have been taken into the system; so it should not be considered as a disease in itself. It may, however, occur without being associated with any other abnormal condition which can be discovered. It is then called tremor simplex or tremor essentialis. The tremor of old age (tremor senilis) comes under this head.
Tremor is sometimes hereditary, and may exist from early life. I have a patient in whom there is a trembling of the hands which has lasted since childhood. This lady's mother and grandmother both had the same form of tremor, and one of her own daughters also has it. In this case the trembling is most marked when voluntary movements are attempted, but it does not materially interfere with writing, sewing, or any other act she wishes to accomplish. There is slight tremor when the hands are at rest.
Tremor simplex is seen in hysteria. In this disease it affects the hands and the facial muscles as well. It is not uncommon in these cases to find the tongue tremble excessively when protruded.
Tremor from chronic poisoning is usually from the absorption of lead, mercury, or some of the narcotic drugs or alcohol. Lead tremor is to be looked for among persons who are exposed to the action of lead, such as painters, printers, or manufacturers of white lead.1 Such persons generally have had some other symptom of lead-poisoning, such as colic or paralysis. The tremor, however, may be the only symptom of saturnine poisoning. Mercurial tremor is not so often seen. It occurs in looking-glass makers or those who work in quicksilver, and may also be a result of the medicinal administration of mercury. The tremor from the excessive use of alcohol or opium is familiar to all. Tobacco, if used immoderately, also causes trembling in the hands. Tea or coffee may have the same effect. There are other drugs which, when taken for a length of time, are liable to cause tremor. Quinine is one of these.
1 Lead in hair dyes or in cosmetic powders often gives rise to plumbism by its absorption by the skin.
Exhausting diseases, like the fevers, or any conditions which enfeeble the system, cause tremor which occurs in voluntary effect. I saw a lady some years ago who was greatly weakened by a malignant growth. She was extremely anxious to sign her name to a legal paper, but, although the hand was perfectly quiet when at rest, when she attempted to write the first letter such intense tremor came on that it was impossible for her to make any mark which was legible.
Tremor follows violent bodily exertion or mental excitement. The action of cold or the chill of intermittent fever is accompanied with an extreme degree of trembling, which we all know. Tremor is also a result of neuritis, but in this case it is associated with other symptoms.
SYMPTOMS.—Tremor is met with as a fine or a coarse trembling. We may also find a fibrillar tremor, such as exists in progressive muscular atrophy. Tremor is divided by some (Van Swieten, Charcot, and others) into two classes: the first is where the tremor occurs while the part is at rest; the second is where it comes on during volitional muscular movements. The former has been termed by Van Swieten tremor coactus, because he believed that it arose from an irritation which affected the nervous centres in an intermittent way. The latter he conceived to depend upon a defect of stimulus, the result of an insufficient amount of nervous fluid, which causes contraction of the muscles under the influence of the will. This he called tremor a debilitate.2
2 Charcot, Lectures on Diseases of the Nervous System.
In paralysis agitans we have an example of tremor coactus, and in disseminated sclerosis, where the tremor occurs only as muscular effect, it belongs to the variety of tremor a debilitate. Those divisions, however, are of but little importance.
When tremor first begins it is slight in degree and extent, and occurs generally only on voluntary effort. Later there may be a constant trembling even when the part is at rest. Beginning usually in the hands, it may extend to the head and legs. It is seen in the tongue and facial muscles after the disease has lasted for some time.
In some cases the trembling can be controlled to some extent by a strong effort of will. The tremor from alcohol or opium is most marked when the individual has been without the use of the stimulant for a short time, and the trembling may be temporarily checked by renewing the dose of alcohol or opium as the case may be.
The muscular trembling from plumbism and mercurial poisoning is more violent than the other forms of simple tremor, and often resembles the tremor of paralysis agitans. In toxic tremors there are often secondary paretic symptoms and indications of other disturbances of the brain and nervous system.
In simple tremor there is no loss of muscular power, and the electrical reactions of the affected muscles are not abnormal. The duration of simple tremor is almost always great. Usually it persists throughout life, becoming more general and more intense as the subject of it grows older. The tremor of hysteria is shorter in duration. Occasionally there are seen cases of simple tremor, which are apparently the result of some trivial cause in a nervous person, which last but a short time.
I have seen a case of tremor of the head in a woman of about forty years, in which the trembling ceased entirely after it had lasted several weeks. Hammond3 describes what he calls convulsive tremor. Under this name he includes cases of non-rhythmical tremor or clonic convulsions, which are unaccompanied by loss of consciousness, but are paroxysmal in character. Pritchard in 1822 presented an account of this affection and related two cases; Hammond mentions six cases. The affection is characterized by paroxysms of violent and rapid convulsive movements, which are more or less general and occur many times a day. The seizures last from a few minutes to several hours.
3 Diseases of the Nervous System, p. 696.
The PROGNOSIS in convulsive tremor seems to be favorable.
Tremor may be regarded as a form of clonic spasm. It consists of slight intermittent contractions of individual muscles or groups of muscles. Fibrillar tremor, such as is seen in progressive muscular atrophy, depends on contractions and relaxations of the muscular fibrillæ, and can be seen under the skin, but does not cause any movements of the limb.
There are no pathological data for explaining what portions of the nervous system are the seat of disease in simple tremor. In experiments upon the lower animals it has been found that trembling occurs in muscles which have been separated from the nerve-centres by division of the nerve. So too in man: when there has been a wound or section of a nerve accidentally, there is likely to be tremor in the muscles which it supplies.
The tremor does not begin at once on section of the nerve, but comes on after a few days. As the peripheral end of the nerve undergoes degeneration the tremor increases. It may last months or even years.
In some of the conditions where tremor occurs the influence of the will is weakened or is entirely absent. This is seen in hysterical trembling and in the tremor of old age as well as in those cases where there is general enfeeblement of the body, as in the fevers.
Trembling is connected with disease of the pyramidal tracts, because in this way the influence of the cerebral centres is withheld from the muscles. When a muscle is in a condition of tonic spasm, it is the result of the running together of very rapidly-repeated muscular contractions. It is like the contraction in a muscle from an interrupted electrical current. If the interruptions are slow, the muscular contractions are seen at intervals like a tremor; but if the interruptions are rapid from frequent vibrations of the hammer of the instrument, then the contractions in the muscle are fused together, as it were, and the muscle is in a state of tonic spasm.
It is held by some writers that tremor is caused by the want of balance between the cerebrum and cerebellum. When, for example, the control of the cerebrum is enfeebled the action of the cerebellum is so great as to bring about tremor by its uncontrolled power.
If we accept the first view, we must consider the tremor as a preliminary stage of paralysis; for the lesion, which at first is slight and causes only an interruption of the conduction of impulses from the brain to the muscles, as it becomes more extensive totally prevents conduction, and paralysis ensues.
Hughlings-Jackson's view, that general convulsions are the result of discharges from the cortex of the brain, and that the tonic contractions of tetanus are caused by discharges from the cortex of the cerebellum, may be applied to the pathology of tremor as well. When, for instance, in a disease like disseminated sclerosis a voluntary effort instead of causing a steady muscular contraction results in irregular spasmodic contractions and relaxations of the muscle, we may imagine that a series of discharges were taking place from the cortex of the cerebellum as long as the voluntary efforts were persisted in. On the other hand, in paralysis agitans it is more probable that a lack of conducting power in the pyramidal tracts prevents the influence of the centres being continuously exerted upon the muscles through their motor nerves.
It is probable that in simple tremor the lesion is situated in the spinal cord; for in this disease we seldom see any evidences of cerebral disturbance. There are no paralytic or psychical symptoms, and no vertigo. In toxic tremors the disease is no doubt located in the brain, for accompanying the trembling resulting from alcohol, opium, mercury, and other drugs are mental changes and more or less muscular enfeeblement.
TREATMENT.—Should the tremor depend upon some cause which can be discovered, of course the obvious course is to attempt to remove the source of trouble. The effort is of greater or less success in different conditions. The tremor from mercurial poisoning sometimes yields to treatment which is directed to the elimination of the mercury. The free administration of the iodide of potassium is the best means to be used, and is often successful. The same means are available in lead tremor. Of course the patient must be removed during treatment from the risk of further absorption of the poisonous substances.
In simple tremor many remedies have been recommended, but the results of treatment are not encouraging. Baths of various kinds and galvanism have been used, and many drugs are advised. Hyoscyamus and its alkaloid, hyoscyamine, have enjoyed a high reputation, and good results have been reported from their use. I have seen relief, but not cure, from their administration. Arsenic is a more reliable remedy and it may be used hypodermically. Eulenburg4 has used this method with good results. I have given arsenic per orem with beneficial effects in cases of simple tremor. In a case to which I have referred above the tremor was relieved while the patient was taking Fowler's solution, and on changing to hyoscyamus the trembling got worse. On returning to the arsenic the symptoms improved, and finally the tremor ceased after the remedy had been taken for some weeks. Hysterical tremor requires that the hysteria should be relieved. Franklinic electricity sometimes controls the tremor in these cases.
4 Ziemssen's Cyclopædia, vol. xiv. p. 392.