The Craniosacral System

The Craniosacral System is a recently discovered physiological system. It is a semi-closed hydraulic system contained within a tough waterproof membrane (the Dura Mater) which envelops the brain and the spinal cord. An important function of this system is the production, circulation and reabsorption of Cerebrospinal Fluid (CSF). CSF is produced within the Craniosacral System and maintains the physiological environment in which your brain and nervous system develop, live and function.

Normally, the production and reabsorption of CSF within the Dura Mater produces a continuous rise and fall of fluid pressure within the Craniosacral System. The semi-closed hydraulic system expands and contracts to some extent with this rhythmical pressure fluctuation. This volumetric accommodation prevents pressure from building up too much within the Craniosacral System. If for some reason your body is unable to accommodate these pressure changes, the subsequent buildup of pressure can contribute to dysfunction and ill health, especially in the Central Nervous System which is enclosed within the boundaries of the Craniosacral System.

Investigation in this field was begun in the second decade of the twentieth century by William G. Sutherland, DO. Dr. Sutherland was influenced by his teacher, Dr. Andrew T. Still. Dr. Still is the founder of Osteopathy; founding Kirksville Osteopathic College in 1892. Key concepts of Dr. Still’s influence Osteopathy and current-day CranioSacral Therapy. Dr. Still’s concepts as identified by Dr. Upledger are:

1. The body functions as a dynamic unit.
2. Structure and function are interrelated.
3. The body has a self-regulating system which tends towards homeostasis.
4. Drugs may be harmful.

Areas of aberrant cranial bone motion were induced and corrected by manual techniques. Soon therapeutic techniques were devised to correct abnormal cranial bone motion.
Early exploration of cranial manipulation was performed primarily by osteopaths and chiropractors who formed societies to investigate and teach cranial methods. These pioneers were at odds with the larger scientific community, and often with their own peers, over one central aspect of the cranial system: the movement of the cranial bones.

Conventional anatomical wisdom taught that cranial bones were movable only in young infants and were solidly fused in adulthood. The controversy raged on until quite recently.
In the mid 1970s, the College of Osteopathic Medicine at Michigan State University sought to resolve this controversy. It brought together a team of researchers led by Dr. John Upledger. Their objective was to prove or disprove the basic tenets of cranial manipulative techniques. The major premise involved the movement of cranial bones.

By studying fresh cranial bone specimens rather than the chemically preserved specimens that were studied by previous researchers, the Michigan State University team demonstrated the potential for cranial bone movement. Optical and electron microscopy showed the existence of blood vessels, nerve fibers, collagen and elastic fibers within cranial sutures. There was little evidence of sutural ossification, which would prevent movement of cranial bones in relation to each other.

Further studies conducted by the Michigan State University team utilized radio wave broadcasts between antennae affixed to the exposed surfaces of cranial bones in adult living primates. This work yielded precise measurements of the frequency and amplitude of cranial bone movement.

With the existence of cranial bone motion established, elucidating the mechanisms behind this motion became the next task of the Michigan State University team. It was here that the role of the Craniosacral Dura Mater and Cerebrospinal Fluid were integrated into a comprehensive model of the Craniosacral System. They called it the “Pressurestat Model.” This model is fully described in the section entitled “The Semi-Closed Hydraulic Craniosacral System” in this study guide.

The results from the Michigan State University research influenced the therapeutic application of cranial techniques. Therefore, in your study of CranioSacral Therapy you will continually find this interplay between osseous and membranous aspects of the Craniosacral System.