Biomechanics of the Craniosacral System

The theory of the craniosacral mechanism is based on five elements:

1. The motility of the nervous system

2. The fluctuation of the cerebrospinal fluid (CSF)

3. The reciprocal tension membranes: falx, tentorium (Fig. 4.2), and dura mater

4. The mobility of the cranial bones

5. The arbitrary mobility of the sacrum between the ilia

We do not want to present these five components of craniosacral therapy in detail here, but instead refer the reader to the relevant literature. Nevertheless, for the sake of a thorough understanding, we must describe a few aspects more precisely.

Intracraneal Membranes

Fig. 4.2 Intracranial membranes: falx and tentorium.

The mobility of the nervous system and the fluctuation of the liquor are most likely at least partly responsible for movements of the craniosacral system, that is, they serve as a sort of motion. The interconnected membranes and bones, however, are of prime importance for the harmony of motion patterns.

The cranial dura mater adheres to the inside of the cranial bones with its parietal leaf and is connected with the periost via the sutures. The visceral leaf, in parts broken off from the parietal leaf, constitutes the cerebral membranes. These are arranged in such a way that they force the cranial bones to make very specific movements during a cranial impulse.

The cerebral and cerebellar falx form a vertical sickle in the sagittal plane that runs from the crista galli of the ethmoidal bone along the metopic suture, the sagittal suture, and to the internal occipital protuberance, all the way to the foramen magnum. They form a dividing wall between the cerebral hemispheres, as well as between the cerebellar hemispheres. The falx also connects the ethmoidal bone, frontal bone, both parietal bones, and the occipital bone.

The cerebellar tentorium runs from the clinoid processes along the upper edge of the petrous bone and the inside of the asterion, and then along the occiput up to the internal occipital protuberance. The cerebellar tentorium separates as it were the cerebrum from the cerebellum. The free edge of both sickles is in contact with the corpus callosum for the falx and with the diencephalons for the tentorium. The tentorium connects the sphenoidal, temporal, parietal, and occipital bones.

Fig. 4.2 Intracranial membranes: falx and tentorium.

Cerebral falx -Straight sinus Cerebellar falx

Nuchal ligament

Cerebral falx -Straight sinus Cerebellar falx

Nuchal ligament

Falx And Ligaments Within The Skull

Temporal bone

Mastoid process

Temporal bone

Mastoid process

Anterior longitudinal -

ligament A(|as

Axis

Costa I

Anterior longitudinal -

ligament A(|as

Axis

Costa I

Nuchal Ligament

- External occipital protuberance

-Squama

Nuchal ligament

Lateral atlantoaxial articulation

Interspinal ligament

- Spinous process C7 (vertebra prominens)

Supraspinal ligament

- External occipital protuberance

-Squama

Nuchal ligament

Lateral atlantoaxial articulation

Interspinal ligament

- Spinous process C7 (vertebra prominens)

Supraspinal ligament

Fig. 4.3a, b Nuchal ligament as extension of the falx.

It is significant that the intracranial membranes form the venous sinuses, the venous blood conduits of the brain. Tension in these membranes can affect venous drainage from the head. The two sickles, falx, and tentorium meet in the straight sinus, also called the "Sutherland fulcrum."

The fact that the external occipital protuberance, which corresponds to the internal occipital protuberance inside the skull, serves as attachment point for the nuchal ligament on the outside of the occiput, is remarkable.

Likewise, the transverse sinus, which is formed by the cerebellar tentorium on the inside of the occiput, is located on a line with the superior nuchal line, which serves as attachment point for the trapezius muscle. The nuchal ligament is thus on the outside of the cranium the extension of the falx, and the fascia of the trapezius is the extension of the tentorium (Figs. 4.3-4.4).

The cerebellar falx is solidly anchored to the foramen magnum and from there passes into the spinal dura mater. Similar to the falx and tentorium, the spinal dura mater is formed by a visceral leaf, while the par ietal leaf passes into the periost (or rather, forms it). It hangs loose in the entire spinal cord channel and is only anchored solidly to the vertebrae at certain points. In the cranial section, it is affixed to the foramen magnum and the second cervical vertebra, and is then attached solidly in the sacral region at the level of S1/S2.

The spinal dura mater encloses the spinal cord and follows the peripheral nerves up to the intervertebral foramen, where it passes into the outer cover of the nerves. In the intervertebral foramen it is also affixed to the bone. Furthermore, there are relatively loose attachments at the vertebral bodies via the denticulate ligaments.

The dura mater is the outer envelope of the three meninges, which envelop the central nervous system. While the pia mater lies on top of the nerve mass, the arachnoid mater fills the space between the pia and dura mater, the so-called subarachnoidal space. This is filled with liquor and serves like a water bed for the brain and spinal cord.

Tentorium Wellness
Fig. 4.4 Fascia of the trapezius as extension of the tentorium.

The subarachnoidal space is connected to the ventricles in which the liquor is produced (choroid plexus). Some 95% of the reabsorption of the liquor takes place in the arachnoid villi of the venous sinus. The remaining 5% is reabsorbed via the lymphatic system.

The dural system is a very resistant membrane that attaches at certain places and forms a hose-like structure filled with CSFand nerves. This means that pressure or tension at one place spreads to the entire system. We can compare this to an air-filled balloon that is compromised in one spot. This pressure can be felt everywhere on the balloon. The entire dural system has five points of attachment whose common anchor is the Sutherland fulcrum:

• In front, the crista galli and clinoid processes

• Laterally, the two temporal bones

• In back, the occipital bone

The fact that pulling on one of these points affects all others via the Sutherland fulcrum is of clinical significance. In other words: a sacral malposition affects the occipitoatlantoaxial (OAA) complex just as much as a malposition in the temporal bone or sphenoidal bone. The consequences are even greater in the spinal column because the sensitive muscle spindles there have an exponential effect.

While the cranial sutures do not permit movement per se, as we know it from the extremities of the spinal column, they do allow for malleability. Movements related to craniosacral impulses do not cause a volume change in the cranium, but only a deformation of the entire hydraulic system including the spinal column and pelvis. Since these movements proceed harmoniously, restrictions in one point of the system manifest everywhere.

If the disturbance is significant enough, the whole system adapts in order to function. This leads to adjustments in the structures, which ultimately causes structural or postural changes. This is the meaning of the term "reciprocal tension membranes" (Fig. 4.5)

Note: Opinions differ on the trigger of craniosacral movements. In general, it is assumed that fluctuations in the liquor cause tensions in the dural system that in turn affect the bones. The special anatomy of the cranial sutures and the attachments of the dura are responsible for specific movement patterns.

magnum

Sacrum

Dura Mater Attachment Foramen Magnum

Clinoid processes

Petrous part of the temporal bone

Reciprocal Tension Membrane

magnum

Sacrum

Clinoid processes

Petrous part of the temporal bone

Fig. 4.5a, b "Reciprocal tension membranes" with attachments.

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Responses

  • lanny cummings
    What ligament attaches to the external occipital crest?
    7 years ago

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