The brain is surrounded by a watery substance called cerebrospinal fluid (CSF), which is produced in chambers called ventricles located in the middle of the brain. In the MRI image on the right, the brain is white and CSF is black. The CSF pathways for the most part are smooth and there are no obstructions.
CSF volume and pressure in the brain change with the contraction and relaxation cycles of the heart. When the heart contracts, a large volume of blood in the arteries is driven into the brain. To compensate for the increase in arterial blood volume a proportionate amount of venous blood and CSF is squeezed out of the cranial vault and into the spinal canal.
The outflow of blood and CSF is affected by the design, dimensions and alignment of the foramen magnum in the bottom of the skull and the spinal canal of the upper cervical spine. Many inherited (genetic) and acquired conditions of the base of the skull and upper cervical spine can decrease blood and CSF flow through the foramen magnum and upper cervical spine. Inherited conditions include: Arnold-Chiari malformations, Dandy-Walker syndrome, craniosynostosis, Klippel-Feil (fused cervical segments) occipitalization (fused upper cervical spine and skull), as well as others. Aquired conditions include aging and injuries. Aging causes muscles, bones and connective tissues to degenerate, which can affect the tunnels nerves and blood vessels pass through. Injuries cause similar problems and hasten degeneration associated with aging.
Cervical spondylosis is a general term used to describe degenerative conditions of the cervical portion of the spine. Spondylosis can also occur in the thoracic and lumbar spine as well. All forms of spondylosis affect the design, dimensions and alignment of the spinal canal. The spinal canal is a tunnel that contains the spinal cord. It also contains arterial blood vessels that supply the spinal cord with fresh oxygenated blood and the verebral venous plexus, which is a dense network of veins, that drains the spinal cord and brain. The remainder of the space is filled with loose fat.
After passing through the foramen magnum and spinal canal of the upper cervical spine, venous blood and CSF that has been squeezed out of the brain during contraction of the heart and exhalation must flow through the lower cervical spinal canal. In the picture above on the left the brain is black and CSF is white. If you look closely at the cervical spine you will notice that the spinal canal is constricted due to spondylosis. In medical terms it is called stenosis, which means narrow. The cause of the stenosis in this case is spondylosis (degeneration of the spine).
In a previous post called CSF, Cisterns, Clapotis and Cysts, I discussed seawalls and standing waves called clapotis. The picture on the right is of Thunder Hole in Acadia National Park off the coast of Maine in North America. Over time the ocean eroded the shoreline and formed a tight canal. The water speeds up as it passes through the tight canal and crashes into the wall at the end causing it to sound like thunder and shoot straight up into the air.
Alterations in the design and dimensions of the lower cervical spine such as from cartilage and connective tissue degeneration can affect blood and CSF flow in the spinal canal similar to land masses that jut out into rivers. Land masses and seawalls reflect incoming waves that then travel back out to sea. When they meet up with another incoming wave the two combine and form a standing wave that is twice the size of the individual waves.
If the design and dimensions of the cervical spinal canal are correct, the blood and CSF will flow smoothly with little resistance. If the path is obstructed by cervical spondylosis (degeneration) their flow will become turbulent. If it becomes sufficiently restricted and turbulent it will cause back pressure and standing waves to form in the brain. Overtime, standing waves can tear apart shorelines. They can similarly damage the brain.
The first areas to receive the brunt of the standing waves are the basal cisterns of the brain. The cisterns are dilated pouches in the subarachnoid space in the outer coverings of the brain. The cisterns are filled with CSF and protect the brain from contact with bones of the base of the skull. The subcompartment in the base of the skull, called the sella turcica for the pituitary gland is also affected. An increase in CSF volume and pressure in the cisterns and sella turcica can cause problems in the brainstem and pituitary gland. It may also explain why some patients with neurodegenerative diseases have problems with the autonomic nervous system referred to as dysautonomia.
Standing waves may play a role in Dandy-Walker syndromes, Arnold-Chiari malformations, arachnoid cysts, empty sella syndromes, multiple sclerosis, Parkinson’s disease, Shy-Drager syndrome, Alzheimer’s disease and other neurodegenerative conditions.
For more information on spondylosis visit my website http://www.upright-health.com/cervical-spondylosis.html .