The Craniosacral System

The word craniosacral refers to two structures of the body, the cranium (skull, head) and the sacrum, the large triangular bone at the bottom of the spine.

To avoid confusion, I will refer to the bones housing the brain as the cranial bones, and the bones that make up the face (facial skeleton) as the facial bones.  The mandible is considered a separate bone but I’ll include it as a facial bone.

The cranium and the sacrum are the endpoints of the craniosacral system.  Between these two endpoints lies the central nervous system (CNS), which consists of the brain encased by the cranium, and the spinal cord housed and protected by the vertebral column (spine).

Extensions of the CNS are the cranial nerves which exit the skull through small openings called foramina, and the spinal nerves which leave the spinal cord and exit the vertebral column through small openings called intervertebral foramina.  The cranial nerves and the spinal nerves are referred to as the peripheral nervous system (PNS).

The craniosacral system is a term used in cranial osteopathy and craniosacral therapy.

Its main components are the brain, the spinal cord, the meninges, the ventricles, the cerebrospinal fluid, the cranial and facial bones, and the sacrum.

The interconnection between these structures was first discovered and appreciated by Dr. William Garner Sutherland, whose teacher was Dr. Andrew Taylor Sutherland, the founder of osteopathy.

As a student of osteopathy, Dr. Sutherland learned to palpate the tissues of the body and develop the ability to sense with his hands the motion of these tissues.  He learned to feel for restrictions in the motion of all the tissues of the body and then help the body to release them to regain health and balance.

This is the original premise of osteopathy as conceived of, practiced, and taught by Dr. Andrew Taylor Still.

Further study led him to extend this training and knowledge to the cranium, and eventually to the spinal cord all the way down to the sacrum.  Many experiments on his own head taught him the relationship between cranial and facial bone motion and a myriad of symptoms, when that motion was disturbed.

Dr. Sutherland’s application of osteopathic techniques to release restrictions in the skull bones became later known as cranial osteopathy.  Dr. Sutherland insisted that cranial osteopathy was an integral part of osteopathy itself, not separate of it.

A brief overview of the component parts of the craniosacral system.

The skull is made up of 22 bones (7 cranial bones and 15 facial bones) with intricately designed edges that allow for individualized movement between them.  They are connected at these edges via a tough membrane in the form of sutures.

Moreover, all but two of the cranial bones have direct connections to one or more of the facial bones.  Thus cranial bone motion affects facial bone motion and vice versa.

The skull is lined with a very tough connective tissue, the meninges, which not only contains the brain and spinal cord, but also subdivides to separate the cerebrum into the left and right cerebral hemispheres.  This subdivision also creates a “downstairs” compartment for the cerebellum and partially divides it into two lobes.

The ventricles are hollow spaces, like little caves, inside the brain, where the cerebrospinal fluid is pumped into the brain continuously.  This fluid then finds its way into every crevice of the brain and down and around the spinal cord all the way down to the sacrum, where the spinal cord has its final attachment.

What follows below is a more detailed look at these components.

The skull and facial bones communicate with one another.

The cranium is composed of seven bones:

  • the occiput
  • the frontal bone
  • the right and left temporal bones
  • the right and left parietal bones
  • the sphenoid bone.

The 15 facial bones are:

  • the ethmoid bone with direct connection to the brain via its cribriform plate
  • the right and left inferior concha
  • the right and left nasal bones
  • the vomer
  • the right and left lacrimal bones
  • the right and left maxillary bones
  • the right and left zygomatic bones
  • the right and left palatine bones
  • the mandible

The cranial and facial bones connect with one another as follows:

The Cranial Bones:

  • The frontal bone connects with the parietal bones, the sphenoid, the zygomatic bones, the ethmoid bone, the maxillary bones, the nasal bones, and the lacrimal bones.
  • The parietal bones connect with the frontal bone, the occiput, the temporal bones, and the sphenoid.
  • The occiput connects with the parietal bones, the temporal bones, the sphenoid bone.
  • The temporal bones connect with the occiput, the parietal bones, the sphenoid, the zygomatic bones, and the mandible (via the temporomandibular joint — TMJ).
  • The sphenoid bone is the master bone because of its central location within the skull, as well as for its connections with all the other cranial bones.  The sphenoid has direct connections with the frontal bone, the parietal bones, the temporal bones, the occiput, the ethmoid bone, and the zygomatic bones.

I won’t belabor the point by listing all the connections of the facial bones.  Many of them are already included in the list above.  It is, however, abundantly clear what an intricate and marvelous arrangement of 22 bones the skull is.

It is important to remember that these twenty-two bones are directly and indirectly connected with one another.  Hence, trauma to the face or the head can partially lock up one bone or more and result in impaired bone motion. This impaired bone motion is ultimately transmitted to the meninges inside the skull and may result in pressure on various brain structures.

Symptoms such as headaches, blurry vision, impaired smell and taste, digestive issues, difficulty swallowing or talking, and altered heart and breathing rate may result in addition to mental fogginess, impaired memory, decreased focus, anxiety, and emotional distress.

The three-layered meningeal system

The meninges, a type of connective tissue, enclose the brain and spinal cord (CNS) as one unit like a tightly fitting stocking.  There are three layers of meninges, called the dura mater, arachnoid mater, and pia mater.

The dura mater is the most outer layer, very tough, and lines the inside of the skull, as well as attaches to the first two neck vertebrae, and the bottom of the sacrum, where it joins with the coccyx (tailbone).

The arachnoid mater is the middle layer and adheres to the dura mater.  It also has web like attachments to the innermost layer, the pia mater.

The pia mater is very thin, transparent, but tough, and covers the entire brain, following it into all its crevices (sulci).

Because of these intimate connections between these three layers, any trauma from the outside of the skull, or from within the skull, such as bleeding in or around the brain, tumors, infections, or hydrocephalus, will be transmitted to all layers.

The tough dura mater creates compartments for the cerebrum and the cerebellum.

The dura mater, a very tough membrane, separates the inside of the skull into three main compartments:  an upper one (two rooms) which houses the two hemispheres, and a lower one, which  contains the cerebellum.  The two rooms upstairs are created as the dura separates the cerebral cortex into the two hemispheres.  This portion of the dura is called the falx cerebri.

The dura also supports the two hemispheres by forming a tent-like structure (the tentorium) above the cerebellum.  Thus, the dura separates the cerebral cortex from the cerebellum.  Moreover, the dura partially separates the cerebellum into two hemispheres.  This structure is the falx cerebelli.

The dura mater also separates the pituitary gland from brain.

Another fact often overlooked:  the tentorium covers the sella turcica (an indentation in the sphenoid bone), which houses the pituitary gland.  This gland, called the master gland,  controls all hormonal actions in the body. Moreover, it has feedback loops to the hypothalamus and the limbic system (emotional brain).

Trauma to the head may distort this part of the tentorium and thus exert pressure on the pituitary gland, potentially resulting in a variety of hormonal disturbances, as well as emotional distress.

The cerebrospinal fluid buffers, nourishes, and detoxifies the central nervous system.

The cerebrospinal fluid starts its journey through the CNS in the first and second ventricles, also called lateral ventricles, where it is pumped in by a group of specialized cells (choroid plexus).

From the first and second ventricles, cerebrospinal fluid moves through the third and fourth ventricles, and from there into the subarachnoid space, which surrounds the entire brain, as well as the spinal cord.  It rejoins the venous system via the arachnoid granulations and dural sinuses.  Remember, that the subarachnoid space is formed by the arachnoid mater and pia mater.

The ventricles are like little caves inside the brain.

The ventricles are relatively large hollow spaces within, and formed by, the brain tissue.

For example, the corpus callosum, a broad band of nerve fibers that connects the two hemispheres, forms the roof and front walls of the lateral ventricles, while the thalamus forms the side walls and the hypothalamus the floor of the third ventricle.  The limbic system (the “emotional brain”) has a similar shape as the ventricles and is nestled around the ventricles.

Pressure changes in the cerebrospinal fluid can wreak havoc with your health.

Since cerebrospinal fluid flows around the brain and through the ventricles (brain cavities), and is contained within the meninges, any distortion of the meninges, or any displacement of brain tissue (tumors, aneurysms, hematomas, infections, hemorrhages, etc) impedes the normal inflow  and outflow of the cerebrospinal fluid, and may result in increased intracranial pressure or hydrocephalus.

A shifting and/or fracture of the cranial bones from head trauma may distort the shape of the cranium and thus the space through which the cerebrospinal fluid flows, also possibly resulting in increased intracranial pressure or hydrocephalus.

A cerebrospinal fluid buildup can cause many seemingly unrelated symptoms.

A cerebrospinal fluid buildup (and pressure on the surrounding brain tissue) in the brain, such as around the cranial nerves, which exit the skull through the meninges, may result in symptoms such as headaches, vision changes, nausea, vomiting, respiratory changes, emotional disturbances, impairment of mental functions, and hormonal changes, among others.

This explains in part why people with head trauma often experience such a myriad of symptoms, some of which seem unrelated to the trauma itself.  Some of these symptoms may not show up until days, weeks, or months later.

CSF trapped within the ventricles by a mid-line shift of the brain tissue due to head trauma, tumor, hemorrhagic stroke, or abscess may cause hydrocephalus, a potentially life-threatening condition.

A decrease in cerebrospinal fluid pressure is just as detrimental to your health.

A tear in the meningeal sac anywhere inside the head or along the spinal cord results in a cerebrospinal fluid leak (CSF leak).  Since the CSF buffers the brain like a shock absorber, a CSF leak decreases this buffering action, like a flat tire, resulting in a bumpy ride for the brain.

If the CSF leak is severe enough, the brain stem starts sagging through the magnum foramen, the opening in the base of the skull through which exits the spinal cord.  This puts pressure on the brain stem itself and the cranial nerves which exit from it.

The symptoms experienced by people whose CSF is leaking reflects the functions of these cranial nerves.  Thus a person might experience blurry or disturbed vision, double vision, impaired balance, dizziness, sound distortion, and nausea.

Other brain structures may be affected by the displacement of the brain stem and change in CSF fluid.  Thus, people may also experience difficulty with focus and memory, as well as decision making.  Moreover, anxiety may develop either as a result of the symptoms or because the limbic system (emotional brain) is affected as well.

Trauma to the brain stem, if severe enough, can put a person into a coma and ultimately result in death.  Hence, a severe CSF leak can be dangerous not only to your health but cause death.

The sacrum can affect CSF fluid motion.

Since the spinal cord is attached to the sacrum via the filum terminale, trauma to the sacrum may partially immobilize the sacrum at one of its two sacroiliac joints or the lumbosacral joint, slowing down or disrupting the CSF fluid motion.

Moreover, since the filum terminale is part of the meningeal sac that contains the brain and spinal cord, a locked up sacrum may tuck on the meningeal sac causing disturbed CSF fluid motion and pressure.

This disturbance may easily be transmitted up the spinal cord and into the brain, resulting in headaches and various symptoms, depending on which brain structures are affected by this disturbance.

The state of the craniosacral system is vital to your mental, emotional, and physical health.

While the brain is the human computer which oversees the processes and activities of every cell in our bodies, the spinal cord is literally the highway of the nerves coming form the brain and going back up to the brain.

Since the brain and the spinal cord (CNS) are the central components of the craniosacral system, it is of utmost importance that we keep this system in the best state possible.

Craniosacral therapy and cranial osteopathy are two therapies that focus entirely on this system and help to maintain it in a healthy state.