Читать книгу Tics and Their Treatment - Feindel Eugène - Страница 15

We must now pass on to elaborate our conception of tic as a disordered functional act.

The term function is employed to denote various biological phenomena differing widely in manifestation and design. Vegetative functions such as digestion, circulation, urination, etc., are regulated by a special unstriped muscle system, the mechanism of which cannot be suspended by cortical interposition; hence under no circumstances can its derangement bring a tic into being.

Other functions, subserved by striped muscles, come within the range of voluntary activity. Some —e. g. respiration – are essential to the maintenance of life, and scarcely to be differentiated from those we have called vegetative. Others, such as nictitation, mastication, locomotion, are no whit less important, since their cessation, in the absence of extraneous aid, would speedily have a detrimental effect on the organism. They too are in a sense vital.

Others, again, such as expectoration, are useful, though not indispensable. Some people labour under the disadvantage of being unable to expectorate, but it is not a fatal defect. The function is not universal.

Finally, let us take once more the case of the child.

As he grows up he passes by easy transitions from the voluntary to the automatic stage. He is taught to swim, and swimming soon rivals walking in the unconcern with which the movements are executed; he learns to write, and no less rapidly does the act become one of unconscious familiarity; his games, his exercises, the labour of his hands – be it digging or typewriting – all reach the level of regular automatism; in short, they are functional acts as truly as locomotion or even respiration, with the qualification of being neither essential nor general.

Such examples serve to illustrate the comprehensiveness of the term functional, and embody all the intermediate forms between what is inherently vital and what is purely acquired. When we have to deal in practice with a case of functional disease, discrimination is obligatory from the standpoint of prognosis. We are alarmed at our patient's respiratory embarrassment, not at his impaired caligraphy.

A distinction has also been drawn between functional and professional affections, profession being conceived as a function of the individual in relation to society. But the latter term has the drawback of being too exclusive. As a matter of fact, scriveners' palsy is met with in people who, so far from being professional writers, do not use the pen much at all. Nor is it necessary to be a professional pianist to develop pianists' cramp. It would be more accurate to speak of disturbances in "occupation acts," it being understood that these have by dint of repetition acquired the automatic characters of true functional acts.

Let us consider for a moment the salient features and component elements in our conception of function.

First and foremost is repetition. It is an absolute law, this of the periodicity of function, and strikingly exemplified in the case of the circulation, digestion, urination, etc. Regularity of rhythm is no less obvious in the muscular activity of mastication, locomotion, and respiration, and its degree seems to be in direct proportion to the duration and vital importance of the particular function.

The characters of this rhythm may be influenced by various extraneous causes. A painful stimulus makes us blink or quickens our respiration. The will may intervene, to accelerate or retard. The personal factor accounts for individual differences, but for each individual a certain rhythm and amplitude of movement, suited exactly to the end in view and conforming to the natural law of least effort, may be regarded as normal. It is only in pathological cases that this law admits of exceptions, and these we shall now proceed to investigate.

Disobedience to the law in the shape of exaggeration or redundance of purposive movement indicates functional excess. For instance, the object of the function of nictitation is to moisten the conjunctiva. In its evolution the child's unmethodical reaction gives place to the rhythmical automatism of the adult. Perfection is the fruit of education.

But the person whose impetuous and uninterrupted blinking far exceeds the demand of the eye for lubrication is plainly troubled with excess, with "hypertrophy" of function. Herein may consist a tic, and, in fact, a large number of tics are nothing more than functional derangements of this kind.

The execution of a functional act at an inopportune moment constitutes another variety of functional disorder. A smile with no pleasant thought to correspond; a cry, a word, that betoken no precise idea; a gesture to relieve an irritation that does not exist; a chewing movement when the mouth is empty – all are examples of untimely, inappropriate functional acts, which merit the name of tics if in addition they are anomalous as regards rhythm, amplitude, and intensity.

Again, the performance of function is accompanied by antecedent desire and subsequent satisfaction. Authoritative proof of this law is furnished by the case of micturition and of defæcation, although momentary suspension of the function of nictitation or of respiration is also a sufficiently convincing mode of demonstrating its truth. In the case of locomotion and other motor functions a preliminary feeling of need may not be so imperative, but it is none the less constant.

Now, it has been observed already that these are equally conspicuous features in our conception of tic. In so far, then, as the latter is preceded by irresistible impulsion and followed by inordinate content, it may be considered a functional affection.

We cannot, however, dispose of each and every tic as an anomaly of some normal universal function. We have already had occasion to notice a large number of functional acts that are not of general distribution, so-called professional movements, which of course are liable to derangement. Such functional disturbances may be styled professional cramps, spasms, or neuroses; but are they identical with tics?

To attach the majority of them to the tics is, in our opinion, justifiable. They are the clinical expression of abnormalities supervening in a function that has by repetition acquired the automatism of genuine functional acts: they are germane to the tics. In certain points, however, the analogy is not absolute.

Professional cramps are motor phenomena distinguished by arrest of intended movement. Spasm signifies excess of motor reaction, cramp denotes its inhibition. It cannot, then, be said that they present the characteristic features of spasm as we have defined it: they are akin rather to a form of tonic tic of which we shall give instances later.

With this premise, we can identify the professional cramp as a functional anomaly recognisable by defective amplitude and force on the part of the motor reaction. Its most special character is its appearance exclusively during the exercise of the function of which it forms the anomaly. Writers' cramp manifests itself in the act of writing, dancers' cramp during dancing, and so on. We are ready to admit the close affinity of professional cramp to tic, with which it has an additional element in common in its occurrence among the psychically unstable. But, regarded as a tic, it is unique in its dependence on the casual exhibition of the professional act; as long as the telegraphist has no occasion to transmit messages, his occupation cramp will not incommode him in the least.

The great majority of genuine tics, on the other hand, are roused into activity by anything or nothing, and this distinction is fundamental.

With all due recognition, therefore, of the marked resemblances between the two, we shall be well advised in not confounding them under one designation. For want of a better word, we shall use the phrase professional cramp to specify functional disturbances taking place solely during the discharge of professional acts.

One other class remains to be dealt with, consisting of functional acts not merely superfluous but actually prejudicial to him who is at once their creator and their slave. The idea that induced them and the object they have in view are alike irrational.

An individual as he moves his arm one day becomes aware of a cracking feeling in his shoulder-joint, and from the unwonted nature of the sensation emanates the notion that he must have some form of arthritic lesion. Renewal of the gesture is attended with reproduction of the sound. The thought of a possible injury develops and extends until it is an object of constant preoccupation and becomes a fixed idea. Under its malign influence the movement is repeated a hundredfold and with growing violence until it passes into the field of automatic action. It is typically functional in its repetition, in the association of desire and satisfaction; but it originates in an absurd idea, and is actuated by a meaningless motive: its range is exaggerated, its performance irresistible, and its reiteration pernicious. In fact, it is a tic.

We may thus regard tic as an obsolete, anomalous function – a parasite function– engendered by some abnormal mental phenomenon, but obeying the immutable law of action and reaction between organ and function, and therefore just as prone to establish itself as any motor act of the physiological order.