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 cranial bone sutures were intricately beveled to fit together in a way that could support movement between them, and he concluded that they must be designed to support a rhythmic pattern of movements. Using light touch, he observed these cranial movements to occur at a rate of about 14 times per minute, alternating between an inspiration phase when the brain and the cranium get shorter and wider, and an expiration phase when the brain and cranium get taller and narrower. He believed that this cranial respiration was a primary process - “the spark that gives rise to the breath”, that it begins in the brain and then moves through all the tissues. Later Magoun hypothesized that the rhythmic cranial movements were caused by CSF pulse waves resulting from a rhythmic pattern of 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 many local conditions including arterial pulsing as well as functional muscular forces.
In the 1990's research showed that CSF moves in synchrony with arterial pulse waves 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 that this CSF flow moves through a network of tiny perivascular tunnels which cleans out by-products from the neural metabolism and moves them into circulation much like the a lymphatic system for the glial cells. This so-called “glymphatic” system primarily operates during sleep, and it may help explain the importance of sleep. In 2013, using a technique called 2 photon microscopy, researchers verified that this glymphatic flow responded directly to arterial pulsation.
At about the same time, there was evidence that breathing was also involved in CSF flow. Researchers showed that oscillations in CSF pressure in rats were mainly coincident with breathing rather than heartbeat and that changes in airway pressure due to a Valsalva maneuver (exhaling against pressure) affect CSF flow. They found that coughing or expiring air corresponds with downward CSF flow, and inspiration corresponds with upward CSF flow.
Finally, in the February 2015 Journal of Neuroscience, a group of researchers published a paper showing that breathing is indeed the primary pump for CSF flow. 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. Thus it is not a primary but a secondary rhythym. Inspiration causes internal rotation of the cranial bones, and expiration causes external rotation of the cranial bones.
Most medical researchers still do not believe that there is any movement between cranial sutures after childhood. They point out that the intricate fit of the cranial sutures was designed to allow the cranium to deform while passing through the birth canal, and all those except the circum-maxillary sutures later appear to close by ossification (filling in of bone). In dried skulls, there appears to be no movement possible between them.
Medical research has long recognized a pathology called craniosynostosis. Synostosis occurs when 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. When recreated experimentally by stapling together cranial sutures, craniosynostosis disturbs the growth of all the cranial bones in the area.
In theory, partial synostoses could prevent some of the cranial bones from moving in synchrony with the other cranial bones, and such a cranial bone movement restriction could potentially affect local CSF flow in portions of the brain. The brain consistently turns out to be more sensitive than we realize, and it could be affected in many ways that we do not yet understand by changes in the pressure of its housing.
RELAPSE DUE TO JAW MUSCLE FORCES
However, the positions of the bones in the front half of the cranium are controlled by the jaw muscles, and 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 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 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.
In addition, regardless of the variable effects of chewing forces on the bones of the front half of the cranium, the positions of those bones are ultimately determined by thepostural forces of the jaw muscles. While the internal architecture of the bones is determined primarily by the functional forces they receive, their outline shapes and positions 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. 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 spinal canal are very different from those in the cranium. The spinal canal is enclosed by a dural sac rather than a shell of bone. CSF flow travels in wave motion along its length, moving downward during systole and upward during diastole. This CSF flow in the spinal canal is weaker than its flow in the cranium, and its flow velocity decreases further as it moves down the spine. Thus the relatively high pressure pulse waves and velocities in the cranial and cervical subarachnoid spaces diminish significantly downward into the spine, with little or no flow near the bottom in the relatively large subarachnoid spaces of the lumbar cistern. Without valves in the glymphatic system to produce negative pressure that brings CSF back up out of the lumbar cistern, the system may be dependent on lying down to allow adequate CSF drainage.
In the spine, we know the effect of blockages to normal CSF flow due to Chiari malformation, spina bifida, a cyst, spinal cord tethering, space occupying lesions, trauma, or infection. Imaging of these blockages by MRI and myelography show that flow is impaired immediately above and below the block. Distal to the block, CSF flow resumes with epidural and cord pulsation. In minor blockages, the flow reflects local turbulence and eddies. In major blockages, the flow may become sufficiently attenuated to become nearly stagnant. Removing the source of the blockage restores the flow and eliminates the symptoms. It's possible that spinal manipulation could restore flow in certain areas. However, any effect of spinal manipulation on cranial respiration is likely to be very small, because the flow of CSF is much weaker in the spinal canal than in the cranium.
In the near future, imaging will help us understand the flow of CSF in the brain and spinal column. We can already image stagnant CSF in the spinal column. Soon it will be more accurately imaged, and manipulation of the cranium or spine will be coordinated with real time measurement of CSF flow. We will be able to determine by imaging if there are any areas of stagnant CSF flow in the brain, and we will be able to study how manual manipulation might be able to change that flow.
Craniosacral treatment apparently helps many people; but the benefits it produces are probably due more to enhancing the range of motion of the spinal segments and removing blockages to their physiologic movement patterns than to enhancing the cranial respiratory rhythym. 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.