by Michael Kern
The bones of the adult skull fit together like an intricate jigsaw, producing over 100 sutural articulations. They are like the tectonic plates of the earth’s crust that shift on the earth’s surface according to deeper forces, which make them move.
Axes of rotation
Traditionally, the primary respiration of each bone is described in relationship to how it moves around imaginary lines called axes of rotation. All the bones of the body express motion in specific ways around a particular axis. An axis of rotation can be located in any of three planes (see Figure 3.15):
Anterior-posterior axis—an imaginary line from front to back.
Horizontal axis—an imaginary line from side to side.
Vertical axis—an imaginary line from top to bottom.
To help picture each of these axes of rotation, use a pencil to play the part of the axis. First, hold the pencil so that the two ends point from your front to back. Then take a small piece of paper and fold a crease along the middle of the paper. Rest the crease of the folded paper on the pencil and rotate it over the pencil. This is how motion occurs around an anterior-posterior axis. If you then hold the pencil pointing from side to side—left to right—a horizontal axis of rotation for the paper is provided. Finally, hold the pencil pointing from top to bottom to see how motion occurs around a vertical axis. (Don’t forget to keep hold of the paper for this one!) In practice, most bones move around a combination of these axes.
Midline bones
The terms flexion and extension are traditionally used to describe the primary respiration of all the single, midline bones of the body. These motions occur around a horizontal axis of rotation. During the inhalation phase of primary respiration, all single midline bones move into flexion. During the exhalation phase, they move into extension.
Figure 3.15: Axes of rotation (illustration credit 3.15)
To give an example, during inhalation the occiput rocks into flexion around a horizontal axis of rotation located just above the foramen magnum (see Figure 3.16). In this motion, the basilar (front) portion of the occiput moves up, while the squamous (back) portion moves down. During the exhalation phase, the occiput rocks back into extension. Its front part moves down and its back part moves up. At the level of the cranial rhythmic impulse, these motions occur as faster movements of one structure in relationship to another. At the level of the mid-tide these motions are perceived as an inner breathing within the unified field of tissues, fluids and potency.
Spheno-basilar junction
The sphenoid bone and occiput form most of the floor of the cranium. They meet at a cartilaginous joint called the spheno-basilar junction. This joint allows for minimal degrees of motion, even though it usually fuses in adulthood. Dr. Sutherland designated the terms flexion and extension to describe the motion that occurs at the underside of these two bones (see Figures 3.16 and 3.17). Flexion occurs in the inhalation phase of primary respiration and refers to a narrowing of the angle between the sphenoid and occiput at their underside. Extension occurs in the exhalation phase and refers to an increasing of this angle.
Figure 3.16: Inhalation/flexion of midline bones (illustration credit 3.16)
As the sphenoid and occiput express their inhalation/flexion phase, both the greater wings of the sphenoid and the back part of the occiput move down towards the feet (see Figure 3.16). At the same time the spheno-basilar junction rises. During the exhalation/extension phase, the greater wings of the sphenoid and the back part of the occiput rise, while the spheno-basilar junction lowers (see Figure 3.17).
The spheno-basilar junction is considered to be the natural fulcrum or pivot of all other cranial bony movements. In fact, the sphenoid is often thought of as the cog from which all other bones “gear off.” The primary respiration of all the other midline bones in the body is named flexion and extension in relationship to the motion at the spheno-basilar junction.
The other midline bones of the body follow the motion of the occiput, and express their inhalation/flexion, and exhalation/extension by rotating in the opposite direction to the sphenoid (see Figure 3.16). They all express this motion around their individual horizontal axes of rotation. In the skull, the other midline bones are the frontal, ethmoid, vomer and mandible.
Figure 3.17: Exhalation/extension of the sphenoid and occiput (illustration credit 3.17)
Importance of the sphenoid
The sphenoid is endowed with considerable importance in the craniosacral concept. It forms a large part of the anterior floor of the cranium, as well as the back portion of the eye sockets. Many cranial nerves pass through or alongside the sphenoid, and so their function can be influenced by it. Problems with eyesight and facial pain commonly result from the irritation of these nerves. The balanced expression of primary respiration in this area is necessary for the healthy function of these nerves.
The pituitary gland sits in a dip in the sphenoid bone, called the sella turcica (Turkish saddle). The pituitary is gently rocked in its saddle during the phases of primary respiration. This rocking motion is considered to encourage the balanced release of pituitary hormones, by helping to milk the gland.51 I have worked with many patients with various types of hormonal disorders such as infertility, chronic stress and menstrual problems. Many of these people have responded well to craniosacral work at the sphenoid bone which has helped to balance their pituitary function.
Furthermore, the sphenoid has a deep connection to the functioning of consciousness. Hugh Milne suggests that it is the seat of our “inner eye,” concerned with the ability to maintain spiritual vision in our lives.52 If the sphenoid becomes restricted in its capacity to express primary respiration, it may restrict the ability of our consciousness to expand. This condition is often found in states of depression. When motion of the sphenoid is open and free, it can allow for a depth and spaciousness of inner vision.
Paired bones
The terms external rotation and internal rotation describe the primary respiration of all the paired bones in the body. In the cranium, these movements mainly occur around an anterior-posterior (front to back) axis. During the inhalation phase of primary respiration, all paired bones move into external rotation. During the exhalation phase, they move into internal rotation.
The paired bones of the cranium are the: temporals, parietals, frontal, maxillae, palatines, zygomae, lacrimals, nasal bones and nasal conchae. The frontal bone is included in this list because, as well as being a midline bone, it also functions in the same way as paired bones. This is because it originates as two bones that are divided by a suture along the midline, called the metopic suture (see Figure 3.14). The frontal bone usually fuses at this suture by about the age of six, although it remains unfused throughout life in about ten percent of the population. However, even when fused, the remnant of this suture allows for some internal and external rotation. Further descriptions of the primary respiration of each bone can be found in any one of the specialized textbooks on the subject.53
Cranial motility
In addition to the mobility that takes place at their sutures, cranial bones express a fundamental motility. Motility is the direct result of primary respiration being expressed from within; the Breath of Life creating an inner breathing. This is a function of the mid-tide. During the inhalation phase, bones express their motility by expanding and widening from side to side. In exhalation, there is a narrowing from side to side. A natural disengagement (separation) of cranial sutures occurs during each inhalation phase.
Motility is an essential prerequisite to the healthy functioning of a bone. As Dr. James Jealous observes, “Before a bone can have a relationship with another bone on either side of it, it must first have a relationship within itself.”54 The balanced expression of motility and disengagement is evidence of that bone’s healthy functioning.
Inter-connections
All the bones of the skull express a specific pattern of primary respiration, but function in close relationship to each other, similar to inter-con
nected wheel cogs. At the level of the cranial rhythmic impulse, these bones can be perceived as floating like corks on the tide, driven in their motion by a deeper tide and regulated by their underlying membranes. Bone and membrane thus move together with synchronicity. At the level of the mid-tide, a unified field of motion involving the bones and membranes is directly perceived. Consequently, cranial bones can be thought of as just more solid places in this continuity of tissue. They are frequently used by craniosacral practitioners as handles for the palpation and treatment of any problems that involve the underlying reciprocal tension membranes.
If all these tissues are able to express their mobility and motility freely, they allow for the permeation of the Breath of Life and its ordering principle. However, as a result of their connection to other tissues, restrictions of cranial bones can influence the functioning of numerous physiological processes elsewhere. Particularly, the fluctuation of cerebrospinal fluid and motility of the central nervous system may be affected. Similarly, as a result of the unity within the body, inertia that starts in other regions may lead to a restriction of cranial bones.
All bones carry a significance linked to their individual location and function. For example, the maxillary bones at the front of the face are closely connected to the functioning of the eyes, nose, sinuses and mouth. However, stressful forces that impede a bone’s primary respiration may disturb its ability to function healthily. Even though all of the cranial bones have important functions, just the temporal bones are discussed in more detail in the next section to provide an example of what can happen if restrictions are present.
Temporal bones
The two temporal bones are located at the sides of the head and also form part of the cranial floor (see Figure 3.13). They have an exquisite and intricate design. It was the bevelled sutures of the temporals that first struck Dr. Sutherland as being like the gills of a fish, intended for primary respiratory motion.55 The temporals articulate with seven other cranial bones:
1. The occiput
2. The sphenoid
3–4. The two parietal bones
5–6. The two zygomae
7. The mandible.
The temporal bones fill the wedge-shaped spaces between the occiput and sphenoid, and sometimes become jammed together with these two bones. Many important structures can get compressed as a result. Physical trauma, such as a long or difficult birth, is one common cause of this.
Once fluid has drained through the venous sinus system, about ninety-five percent of it exits from the head through two small holes called jugular foramina. These are located in the sutures formed between each temporal bone and the occiput. If either of the jugular foramina become narrowed, fluid drainage from the head can get impaired. Congestive headaches and tiredness commonly result. The jugular foramina also contain three cranial nerves, including the widely influential vagus nerve. The function of these nerves can also be irritated by compression (see also Chapter 5, “Cranial Nerves”). Craniosacral treatment to help disengage this suture can bring about the effective relief of cranial congestion or nerve irritation.
Furthermore, the temporal bones contain the organs of hearing and balance. These faculties can become disturbed when primary respiration is compromised. Problems such as hearing difficulties, tinnitus and dizziness may result. The eustachian tubes, which stabilize air pressure in the ears, can also become affected. This often creates a tendency to ear infections.
The temporal bones also function in close continuity with the reciprocal tension membrane system. The tentorium cerebelli attaches along the petrous ridges at the inside of the temporal bones, and important venous sinuses are contained within these membranes (see Figure 3.9). Venous sinus drainage, as well as problems referred through the reciprocal tension membranes, may result from patterns of inertia.
The mandible (jaw bone) articulates with the temporal bones at the temporo-mandibular joints located just in front of the ears (see Figure 3.13). These are the most used joints in the body, brought into action every time we eat, drink, talk or yawn. The position and motion of the temporal bones directly influence the functioning of the temporo-mandibular joints. A wide range of clinical symptoms can result from problems that affect these joints, including jaw pain, clicking of the jaw, restricted opening of the mouth, dental problems, headaches, neck and shoulder pain, hearing problems, difficulty swallowing, tinnitus, dizziness and facial pain.
In recognition of the widespread consequences that difficulties with the temporal bones may create, Dr. Sutherland referred to them as “mischief makers.”56 However, this is a two-way relationship because these bones not only influence, but can also be influenced by, other parts of the primary respiratory mechanism.
The key point in craniosacral practice is that when primary respiration is restored there is a return to normal functioning of cranial bones and their interconnections, as the relationship with their blueprint for health is re-established.
5) The Involuntary Motion of the Sacrum Between the Iliac Bones of the Pelvis
The word sacrum is related to the word “sacred.” The sacrum is a large, triangular-shaped bone made up of five fused vertebrae. It fits between the two iliac bones of the pelvis, forming the base upon which the rest of the spinal column sits. It articulates with the bones of the pelvis through sacro-iliac joints on each side. This bone is thus the foundation of the spine and helps support the weight of the whole trunk. As such, it plays an important role in the healthy workings of the rest of the spine. Any inertia that affects the sacrum can alter the functioning of vertebrae higher up. This is a common cause of backache.
The sacrum is firmly strapped to the pelvic bones and to the vertebrae just above by strong bands of connective tissue called ligaments. Nevertheless, the sacro-iliac joints are sufficiently flexible to allow for small degrees of motion. A voluntary motion occurs during actions such as walking and running, and an involuntary motion occurs during the different phases of primary respiration. There are no muscles that connect the sacrum to the pelvis, so any motion (voluntary or involuntary) which takes place here has to be created by other causes.
As above, so below
As mentioned, the dural tube is firmly attached at its upper end to the occiput, but then has no firm attachments until it reaches the second segment of the sacrum. This core-link makes the sacrum an integral part of the primary respiratory mechanism. The relatively inelastic dural tube helps to connect the primary respiration of the occiput and the sacrum (see Figure 3.12). As the occiput rocks into inhalation/flexion and exhalation/extension, so the sacrum moves in synchrony. In addition, this involuntary motion of the sacrum is gently impelled by the longitudinal fluctuation of cerebrospinal fluid. Because the sacrum is directly connected to the rest of the primary respiratory mechanism, its motion may easily influence or become affected by these other regions.
Sacral motion
As the sacrum is a single midline bone, its flexion and extension can be described as occurring around a horizontal axis. The axis of rotation for this movement is located at the second sacral segment (S2), where the dural tube is attached. Also, as a single midline bone, the sacrum rotates in the opposite direction to the sphenoid. When it moves into inhalation/flexion, the upper part of the sacrum (called the sacral base) rotates posteriorly and superiorly, while its lower part moves anteriorly (towards the pubic symphysis) and inferiorly (see Figure 3.12). Motility is largely expressed at the sacrum as a widening and uncurling of the bone in the inhalation phase. In exhalation, it narrows and curls up.
Nerve irritation
Nerves that regulate the organs of reproduction and elimination emerge through small openings in the sacrum. These nerves can become irritated if they get compressed, which can happen if the sacrum becomes locked in a certain position. Irritation of the sacral nerves may produce gynecological, reproductive, bowel or urinary tract disorders. Nerves also emerge from the sacrum to form the great sciatic nerve, which controls many muscles of the leg. If
this nerve becomes irritated, it can produce the painful symptoms of sciatica.
The sacrum is subject to a wide range of influences, psychological as well as physical, which can affect its motion. Because of the sacrum’s location and function, feelings of insecurity, issues of grounding, experiences such as sexual abuse or a lack of support are often reflected in its pattern of primary respiration.
THE WHOLE BODY
All parts in the whole body obey the one eternal law of life and motion.57
DR. A.T. STILL
The five core aspects of the primary respiratory mechanism are in direct relationship to the dural membrane system, and are all located near the midline of the body. However, the expression of primary respiration is not limited to these core tissues; it is a whole body response.
Connective tissues
One of the basic principles of craniosacral work is that everything in the body is connected to everything else. The connective tissues of the body are important parts of this integrated system. There is a continuous network of connective tissue from head to toe, and from the core of the primary respiratory mechanism to the periphery of the body. These tissues express primary respiration in certain specific ways.