A study of the rhythmic motions of the Cranium living cranium

The hypothesis of inherent motility of the cranium has been supported by palpation of the living head. The hypothesis that a rhythm synchronous with the arterial pulse and another associated with thoracic respiration might be detected is in accord with known physiologic phenomena. The report of a third palpable rhythm, slower than either pulse or respiration, required more study. This article records a series of experiments conducted with instrumentation suitable for studying minute expansile-contractile motions of the live cranium. The recordings show that there is a cranial motility slower than and distinguishable from the motility of the vascular pulse and thoracic respiration, and that such motion can be recorded instrumentally. Studies of rhythmic cellular function and movement of cerebrospinal fluid have been reported elsewhere. More investigation is needed to establish the relations among the various physiologic phenomena described. Additionally, the clinical significance of the rhythmic motion of the cranium needs documentation. It has been 70 years since Sutherland conceived the idea that the cranial bones are beveled for articular mobility to accommodate the motion of a respiratory mechanism.' His meticulous study of the cranial bones revealed that each bone is beveled reciprocally, with corrugations running transversely, diagonal friction gears, balls and sockets, pintles, pulleys, fulcrums, hinges, and other mechanical arrangements that made provision for movement. Palpation of the living head lent support to the hypothesis, first advanced in 1939, 2 that there is inherent motility of the cranium. It was a plausible contention and in accord with known physiologic phenomena, that a rhythm synchronous with the arterial pulse might be detected, but his report of a third palpable rhythm, slower than either pulse or respiration, needed further study. Does such a motion really occur? Can it be mechanically recorded? If it exists, what is its relation to known physiologic functions? This paper is intended to present the results of exploration of these three questions. With regard to the first question, as to the existence of such a rhythmic motion, slower than and different from the thoracic respiratory rhythm, within the living cranium, those trained in skillful palpation of the human body have claimed for nearly 30 years that such inherent motility is detectable. The validity of the palpatory findings of persons with trained hands is, however, subject to question by those who lack such palpatory skill. The doubt is due primarily to the plausible hypothesis that the sense of touch will experience systematic tactile illusions when subjected to small cyclic motions. It can be shown mathematically that if the pressure-sensing nerve ends are acted on by the sum of two oscillatory pressures of different frequency, and if the effective signal