Cranial and Craniosacral
CRANIAL OSTEOPATHY treats TMJ and other disorders by using light manual pressure to manipulate the skull in order to free up perceived blockages to a rhythmic pulsing that involves each of the skull bones in its own individual movement pattern. Cranial practitioners believe that birth trauma, blows to the head, and even unidentified traumatic incidents can misalign the cranial bones so they no longer move in harmony with the cranial respiratory rhythym, and manipulation using very light manual pressure can restore their alignment. There are many patients who report that the treatment relieved a wide variety of symptoms, however most of those in the medical field do not believe that the treatment has any scientific basis.
Cranial respiration, the theory that forms the basis for cranial work, was hypothesized in the 1930's when an osteopath named William Sutherland noticed that the temporal bone sutures were intricately beveled to fit together in a way that could support movement between them, and he concluded that all the cranial sutures must be designed to support a rhythmic pattern of subtle movements that result from brain movements generating CSF pressure pulse waves at a rate of about 14 times per minute. Later Magoun identified the cause of the rhythmic CSF pulse waves as the secretion of CSF by the choroid plexus. These cranial osteopaths described an elegant system of specific rotations and displacements that each cranial bone should undergo according to this rhythmic pulsing and a series of low force manual manipulations that could be used to correct cranial bones which were not moving freely with the other cranial bones according to that rhythym.
In the following decades, high precision ultrasound and other technologies verified that the skull is not a rigid container but a dynamic living system. It changes shape depending on body posture and gravity. Catheters inserted into the CSF showed that the cranium responds to arterial pulsing as well as functional muscular forces.
In the 1990's researchers showed that CSF moves in synchrony with the arterial pulse, particulary a systolic pulse wave, from its production site in the choroid plexus deep inside the brain through the ventricular system to the exterior surfaces of brain and spinal cord in the subarachnoid spaces, from where it drains into the venous bloodstream and cervical lymphatics.
In the 2000's, researchers discovered the “glymphatic system” - a network of tiny perivascular tunnels that moves CSF through the brain to clean out by-products from the glial cell metabolism and move them into circulation much like the a lymphatic system for the brain. This glymphatic system primarily operates during sleep, when it may be necessary for neurons to eliminate potentially neurotoxic waste products. In 2013, using a technique called 2 photon microscopy, researchers showed that this glymphatic flow responded directly to arterial pulsation.
At about the same time, there was evidence that breathing was involved in CSF flow. Researchers showed that oscillations in CSF pressure in rats were mainly coincident with breathing rather than heartbeat, that changes in airway pressure due to coughing or a Valsalva maneuver (exhaling against pressure) affect CSF flow, and that expiration corresponds with downward brain displacement and inspiration corresponds with upward brain displacement.
Finally, in the February 2015 Journal of Neuroscience, a group of researchers published a paper showing that breathing is indeed the primary pump. Using a real time high temporal and spatial resolution MRI to show all the details of CSF movement in healthy human volunteers, they found that it moved only slightly in synchrony with the vascular pulse; it moved primarily in synchrony with breathing, particularly with inspiration. It could be increased by forced breathing, and it could be suppressed by holding the breath. The authors concluded, "During inspiration, thoracic pressure reduction elicits pronounced CSF flow as it is transmitted to the brain subarachnoid spaces via the interconnected venous plexus around the thoracic spinal column and within the spinal canal... Inspiratory pressure reduction empties the venous plexus and leads to a compensatory CSF flow downward into the spinal canal... The present results provide unambiguous evidence that inspiration is the main driving force for CSF dynamics in healthy human subjects." This research helps explain the clinical findings linking exercise with brain diseases such as Alzheimers.
IMPLICATIONS FOR CRANIAL ADJUSTING
It's interesting that the rate of normal resting breathing is very close to the cranial respiratory rhythym hypothesized by the founders of cranial work. It now seems likely that the cranial respiratory rhythym they detected is actually the result of the pulmonary respiratory rhythym. Inspiration causes internal rotation of the cranial bones, and expiration causes external rotation of the cranial bones. Therefore, theoretically if cranial work is to enable better CSF circulation, it should facilitate internal rotation during inspiration and external rotation during expiration.
Most medical researchers still do not believe that there is any rhythmic movement between cranial sutures after childhood. They point out that the intricate fit of the cranial sutures was designed only to allow the cranium to deform while passing through the birth canal, and in dried skulls it appears that these sutures have closed completely after infancy. Occasionally one of the cranial sutures gets damaged during the birth process or from early childhood trauma, and it later fails to expand in harmony with the surrounding cranial bones. This locking together of sutures is called synostosis. When recreated experimentally by stapling together cranial sutures, craniosynostosis disturbs the growth of all the cranial bones in the area.
It's plausible to consider that some of our patients may have localized or partial synostoses that prevent the cranial bones in the area from moving in synchrony with the other cranial bones, that such a cranial bone movement restriction could potentially affect local CSF flow in portions of the brain, and that manually freeing some of these partial synostoses using gentle manual manipulation could restore their range of movement. However, the effects of such a restoration of range of movement of cranial bones is something that we do not yet understand. The brain consistently turns out to be more sensitive than we realize, and it could be affected in many ways by changes in the pressure of its housing. We can already image stagnant CSF in the spinal column. In the future we will be able to image CSF flow in the brain and study how manual manipulation might be able to change that flow.
RELAPSE DUE TO JAW MUSCLE FORCES
However, any changes in the configuration of the bones in the front half of the cranium which could be produced by light manual pressure would likely be dwarfed by the effects of chewing and swallowing. Biting forces spread very large forces over the front of the cranium hundreds of times each day. Forceful biting bends the entire cranium in monkeys, separating its two halves along the sagittal parietal suture. Pre-industrial humans with strong jaw muscles have a thick ridge of bone along that same suture. Modern humans have weaker jaw muscles, but we also have thinner skulls, and they are probably also bent slightly by functional forces.
The distribution of biting forces in modern human skulls was recorded by researchers using stress sensitive paint, as shown below. The effect of these jaw muscle forces on the cranium explains why chewing stimulates cerebral circulation. The effect of these jaw muscle forces on the cranium also could be expected to produce partial or total relapse of manual manipulation performed with much lighter forces, of at least the temporal and sphenoid bones, unless that manipulation is coupled with a simultaneous change in the bite that alters the way jaw muscle forces are delivered to the front of the cranium.
The outline shapes and positions maintained by bones of the body are determined primarily by the light steady background (postural) tensions of the muscles attached to them. This effect has been well studied in regard to the facial bones in orthodontics. In contrast, the internal architecture of the bones is determined primarily by the functional forces they receive. It seems unlikely that the positions of at least the bones of the front of the cranium could be altered without simultaneously altering the resting postures of the jaw muscles. The positions of the temporal bones are controlled by the resting tensions of the temporalis muscles, and the positions of the sphenoid and maxillary bones are controlled by the resting tensions of the internal pterygoid and masseter muscles. Numerous studies have shown that the resting tensions of these jaw muscles are controlled by the precise contours of the bite.
Craniosacral treatment is a relatively recent extension of cranial work that grew out of studies which showed that bending the spine produces changes in CSF pressure. This finding should come as no surprise, because the spinal column is enclosed in the same CSF reservoir as the cranium. Upledger and other practitioners reasoned that, since the spinal column should be subject to the same blockages of CSF circulation that occur in the cranium, it should be manipulated together with the skull to relieve blockages.
However the hydrodynamics in the space enclosed by the cranium is very different than the hydrodynamics in the spinal canal, which is enclosed by a dural sac rather than a shell of bone. The flow of CSF in the spine has been studied extensively by MRI and myelography to evaluate various pathologies that affect the spine. These studies have shown that CSF flow travels in wave motion along the length of the spinal canal. It moves downward during systole and upward during diastole. However, its flow in the spinal canal is weaker than its flow in the cranium, and its flow velocity decreases as the further down the spine. When spinal cord CSF flow gets blocked by conditions such as a cyst or spinal cord tethering, flow is impaired only immediately above and below the block. Distal to the block, CSF flow resumes due to to epidural and cord pulsation. In minor blockages, the flow reflects local turbulence and eddies. In more major blockages, the flow may become sufficiently attenuated to become nearly stagnant. However, these blockages are rarely due to the alignment of the bones, and the bones are not manipulated to relieve blockages.
Craniosacral treatment has grown in popularity and apparently helps many people, but the benefits it produces are probably not due to enhancing the cranial respiratory rhythym but to enhancing the range of motion of the spinal segments and removing blockages to their physiologic movement patterns. Joint health is dependent on the range of motion of the surrounding bones, and anything that increases the range of motion at a joint is likely to help it heal. The cranial base functions as an extension of the spine into the cranium, therefore holding the occiput in one hand when a patient lies on a table enables a therapist to feel the mobility of the spinal column and manipulate it to enhance its range of motion.