Patterns of Tremor in Normal and Pathological Conditions

Abstract

This is an electromyographic study of voluntary tremor, tremor due to adrenalin and fatigue in normal subjects and spontaneous tremor in Parkinsonian patients. Simultaneous action currents of the biceps, triceps and brachio-radialis muscles were recorded on a Grass inkwriter, employing surface electrodes. The electrodes consisted of drops of a mixture of 25% plaster of paris and 75% modeling clay applied as a thin paste made up with salt solns. A bare Cu lead-wire terminal was inserted into each pellet before setting. Records were taken at rest, during voluntary or involuntary tremor, with various arm postures, and during various degrees of flexion and extension freely or against resistance, or under combinations of these conditions. It was shown that tremor may be looked upon as a periodic form of movement, and in many respects its change in pattern with volitional effort follows the rules of voluntary or reflex movement patterns. The manifestations of tremor are those of muscles directly reflecting the activity of the spinal level, while the ultimate occasion of the occurrence of tremor is typically a lesion above the spinal level. The pathological disorganization then is reflected to the otherwise normal spinal level by a change in the tonic influence of the higher centers mediated over the pyramidal of extrapyramidal systems. The fundamental pattern of alternating tremor including spinal clonus, is apparently inherent in the spinal level of function, although the activity of tis physiological components is normally expressed in terms of normal motor movement. It may be looked upon as a release phenomenon, but presumably not as a release of any archaic or primitive pattern of movement. Rather it is the manifestation of a pattern resulting from reflex or volitional activity when certain components normally preventing tremorous expression are more or less deranged or suppressed.