Palpatory phenomena in the limbs: A proposed mechanism

Physiological Mechanisms Underlying the Primary Respiratory Mechanism (PRM) and Cranial Rhythmic Impulse (CRI) in Osteopathy: A Systematic Review

BACKGROUND

Cranial Rhythmic Impulse (CRI) or Primary Respiratory Mechanism (PRM), movement felt on the scalp or the rest of the body, respectively, is a fundamental concept used by osteopaths in their practice for their diagnosis and treatment. However, the physiological basis of this phenomenon remains unclear. Sutherland, the founder of cranial osteopathy, proposed in 1939 that PRM was due to the movement of the cranial bones pulled by the meninges, themselves pushed by the fluctuation of cerebrospinal fluid and the motility of the central nervous system. Since then, Sutherland's theory has become dogma, despite scientific progress refuting it, and few osteopaths have attempted to find better explanations.

OBJECTIVE

This systematic review of Medline, Science Direct and the Cochrane Library indexed electronic databases explores current knowledge of the physiological mechanisms underlying the Primary Respiratory Movement (PRM) or Cranial Rhythmic Impulse (CRI).

METHODS

We entered the following identified keywords: "osteopathy in the cranial field"; "cranial rhythmic impulse"; and "primary respiratory mechanism". We identified 193 studies, evaluated 115, and identified 28 articles that fulfilled our criteria. We classified the studies in terms of methodological rigor, types of studies and tools used. No study had three good-level items, and only five studies had two good-level items corresponding to the type of study and tools used. The protocol of the review has been registered on PROSPERO-CRD42023488497.

RESULTS

Out of the 28 articles, 20 referenced at least one of Sutherland's hypotheses, often quoting the model to critique or challenge it, while 25 of them refer to other hypotheses and/or mechanisms underlying PRM/CRI: 11 concern vasomotion in blood vessels (7) and lymphatic vessels (6), 20 THM waves, 14 heart rate variability, 9 ventilation rate, 2 the extra-cellular matrix and 1 oxidative metabolism.

CONCLUSIONS

Although Sutherland's theory remains prevalent in general beliefs, in scientific literature, THM waves driven by autonomous system activity have gained prominence, emerging as the leading hypothesis. The results from this systematic review confirm the need for a paradigm shift for the CRI/PRM in osteopathy, and for more rigorous evaluation and communication on a model in step with evolving scientific data.

Fascial hierarchies and the relevance of crossed-helical arrangements of collagen to changes in shape; part II: The proposed effect of blood pressure (Traube-Hering-Mayer) waves on the fascia

Periodic changes in arterial pressure and volume have long been related to respiratory and sympathetic nerve activity (Traube-Hering-Mayer waves) but their origins and nomenclature have caused considerable confusion since they were first discovered in the eighteenth century. However, although they remain poorly understood and the underlying details of their control are complicated, these waves do provide valuable clinical information on the state of blood pressure regulation in both normal and pathological conditions; and a correlation with oscillatory motions observed by certain practitioners suggests that they may also have some physiological value that relates to changes in the volume of fascial 'tubes'. Part I of this paper (Scarr, 2016) described a complex fascial network of collagen-reinforced tubular sheaths that are an integral part of muscle structure and function, and continuous with 'higher-level' fascial tubes surrounding groups of muscles, the limbs and entire body. The anisotropic arrangements of collagen fibres within the walls of these tubes reflect the most efficient distribution of mechanical stresses and have been considered to coordinate changes in shape, and a proposed link between cyclic variations in arterial pressure and volume, and the behaviour of these fascial compartments is now described.

Fascial hierarchies and the relevance of crossed-helical arrangements of collagen to changes in the shape of muscles

Muscles are composite structures consisting of contractile myofibres surrounded by complex hierarchies of collagen-reinforced fascial sheaths. They are essentially flexible cylinders that change in shape, with the particular alignment of collagen fibres within their myofascial walls reflecting the most efficient distribution of mechanical stresses and coordinating these changes. However, while the functional significance of this crossed-helical fibre arrangement is well established in other species and in different parts of the body, relatively little attention has been given to this within the fascia of humans; and the relevance of this geometric configuration to muscles and surrounding fascial tissues is described.