FREQUENCY ANALYSIS OF PHYSIOLOGICAL AND NEUROTIC TREMORS

It seems reasonable to assert that the diagnostic distinctions between the common organic causes of tremor emerged clearly during the sixties of the last century, and that this was partly due to the work of Charcot and his pupils. At this time also the Marey tambour (Marey, 1868) came into widespread use. These two circumstances seem to have been responsible for the first attempts to study graphical records of tremor by Charcot's pupils, and it was in turn upon these experimental results that Charcot based his later teaching (Charcot, 1888, 1889) on tremors. He divided the non-intentional tremors into three main groups: (1) Slow, 4-5 per second (Parkinsonian); (2) intermediate, 5A-6 per second (hysterical); (3) rapid or vibratory, 8-9 per second (Basedow's disease, alcoholism, general paralysis of the insane). As far as the tremors of neurosis are concerned, Charcot's later pupils (e.g., Dutil, 1891) were able to show that this scheme was an oversimplification and that hysterical tremors, for example, were often vibratory in type. Since then there has been little advance in our knowledge of the neurotic tremors. Most clinicians have simply divided neurotic tremors into the categories of coarse and fine, corresponding with the intermediate and the vibratory groups respectively. The coarse tremors are commonly associated with hysteria and are often, on the basis of wartime experience, held to carry a better prognosis than the fine tremors, which are commonly associated with anxiety and other neuroses (Mott, 1919). Meanwhile Schafer (1886) had demonstrated a 10-per-second rhythm in the normal human voluntary myogram, and a majority of subsequent authors have found this to be the predominant frequency of physiological tremor. Theories sometimes held to account for this family of physiological and neurotic tremors may be summarized as follows: (a) That the rhythm is determined by the mechanical properties of the muscle or of the muscle twitch; (b) that it is due to the delayed self-correction inherent in the stretch reflex; (c) that there is some intrinsic rhythmical propensity at the spinal level; and (d) that the rhythm is due to driving by higher centres, e.g., the motor cortex. It must be observed that the relationship between " physiological ", emotional, thermal, and neurotic trembling has never been precisely defined. It is therefore not usually possible to be clear as to exactly which type or types of tremor these theories are held to explain. This paper describes the frequency analysis of normal and neurotic tremors, the results of which suggest a common physiological basis. The definition of a neurotic tremor used in this paper is a tremor occurring in a person suffering from neurosis. It will be seen that from the point of view of the harmonic components of neurotic tremors, they are largely an exaggerated form of physiological tremor. The above definition is therefore a logical necessity.