Venous inversion flows is when blood goes in the opposite direction that is was meant to, that is, back into the brain instead of out of it. The part of the skull that contains the brain is called the cranial vault. Skull shape and the design of the cranial vault affects the layout, length, pitch and attachment angles of the veins of the brain called dural sinuses. It is the layout of the posterior fossa portion of the cranial vault that affects the impact of venous inversion flows, called backjets, into the brain.

The outer white lines in the brain scan to the left represent the borders of the posterior fossa which contain the brainstem and cerebellum – two key structures in the brain. The brain scan is from a paper published in Cerebrospinal Fluid Research on 12/18/05 by Raymond F. Sekula, Jr. et al. titled “Dimensions of the posterior fossa in patients symptomatic for Chiari 1 malformamtion but without cerebellar tonsilar descent.”

The dural sinuses are the large drainage veins of the brain. In the brain scan above several dural sinues are located along the two rear white lines that form the back side of the posterior fossa. The top white rear line, which is the top of the posterior fossa, is also the location of the tentorium cerebelli (see the word tentorium). The tentorium cerebelli is made of connective tissue and covers the posterior fossa separating it from the compartments above. An important dural sinus, called the straight sinus follows the course of the tentorium cerebelli. The pitch and angle between the top and bottom lines that represent the rear border of the posterior fossa and the course of the dural sinuses may play a role in the formation of the lesions seen in multiple sclerosis due to venous inversion flows.

In contrast to the image above which shows the borders of the posterior fossa, the image below is an MRI of the veins of the brain injected with dye. It’s called a venogram. The S-like structure near the base of the skull on the right side is called the sigmoid sinus. The long section going to the top of the head is called the superior sagittal sinus. In between these two sections is a shorter section called the transverse section which starts at the top of the S shape and ends at the beginning of the superior sagittal sinus. The sigmoid (S-shaped) and transverse sinus make up the bottom portion of the posterior fossa represented by lines in the first image.

At the junction of the transverse sinus and superior sagittal sinus is a small sinus that runs upward and forward at about forty-five degrees in this individual. It’s called the straight sinus and was mentioned above. In some people the straight sinus’s attachment varies and can be close to a ninety degree angle. The length of the transverse sinus varies as well. As mentioned above the straight sinus follows the cover over the top of the posterior fossa called the tentorium cerebelli represented by the top line in the first brain scan above.

Venous Inversion Flows Versus Backups

Several new theories suggest multiple sclerosis may be caused by venous backups and venous inversion flows into the brain. The first theory proposed by Dr. Franz Schelling suggests that MS lesions are caused by venous inversion flows or backjets from thoracic and abdominal veins into the jugulars and then into the brain, and from the vertebral veins flowing backwards and into the brain. Dr. Schelling attributes the venous inversion flows to several causes. One potential cause is faulty or inadequate valves in the jugular veins. The faulty valves allow the transmission of the normal waves in the blood in these veins called respiratory waves to flow back to the brain. Another cause is due to severe trauma, such as whiplash, causing an acute backward flow of blood into the brain.

In addition to Schelling’s theories, the term I coined CCVBP refers to chronic craniocervical venous back pressure from musculoskeletal disorders. CCVBP can lead to chronic edema (swelling), ischemia (decreased blood flow), normal pressure hydrocephalus (congestion of CSF) and subsequent neurodegenerative conditions and diseases in the brain such as MS. CCVBP can have numerous causes including traumas that cause spinal injury.

The latest theory proposed by Dr. Zamboni is called chronic cerebrospinal venous insufficiency or CCSVI, which simply means poor or inadequate drainage of blood from the brain. Zamboni blames the lack of sufficient drainage in the brain on stenosis of the internal jugular veins in the neck and the azygous vein inside the ribcage.

Where Dr. Schelling’s and Dr. Zamboni’s theories fall short is their inability to explain why the incidence of MS gets progressively lower the closer people live to the equator, and people living at or near the equator have the lowest incidence of MS compared to people living in more northern climates. These theories also fail to explain why, regardless of where they live, Asian and African races have a much lower incidence of MS. Interestingly, it is almost non-existant in Eskimos (who have Asians skulls) despite living in the most extreme northern climates. This brings up the recent news of a suggested treatment regime of Vitamin D for relapsing MS suggesting that the geographical connection mentioned above may be due to lower sunlight conditions. This connection does not explain the lower incidence in Asians and Africans.

CCVBP takes into consideration the difference in the incidence of MS between races, gender and geographic locations and theorizes that it may be due to the difference in the design of the cranial vault and the reaction of the brain and fluids inside the vault during whiplash type trauma.

The posterior fossa is the first place to receive the brunt of the impact of any venous inversion flow. In this regard, a steep straight sinus that creates a more relaxed or open angle between the dural sinuses (veins) where they intersect can predispose a person to more venous inversion flows due to less resistance to backflow. When the intersecting angle is more acute or tighter it helps prevent venous blood from going back up into the brain when certain situations occur.

The inclination of the base of the skull in Europeans tends to tilt upward similar to Asians. Europeans also tend to have tall faces similar to Asians. The base of the skull tends to be shorter than Asians and Africans which are similar in skull design. The smaller design of the base affects the dimensions of the posterior fossa. The tall face and cranial vault combined with a short base predispose European designs to greater penetration of backjets into the brain due to a wider angle at the intersection of the dural sinuses. The prognathic or protruding design of the face further increases the swing weight of the head during whiplash motions causing greater velocity of the movement of blood.

In contrast to European designs, the design of Asian and African skulls more than likely prevents or limits the extent of reverse flows due to the angles, length and pitch of the dural sinuses in the posterior fossa. A sharper angle in the straight sinus would do the same. On the other hand, the larger higher center of gravity in Asian designs may be predisposed to Chiari-like compression of the optic nerve. Similarly, the compact design of the upper portions of the cranial vault may make African designs similarly susceptible to compression of the optic nerve.

I have used the hypothetical analogy before of an Asian, African and European who all suffer severe whiplash injuries due to a car accident they were in while traveling together. A little over a year later the European traveler gets optic neuritis and classic lesions of multiple sclerosis. Shortly after that his Asian and African companions get optic neuritis and transverse myelitis but none of the classic lesions seen in MS. In this case the European is diagnosed as having MS. The Asian is diagnosed with optic spinal multiple sclerosis and the African is diagnosed with Devic’s disease. The question is, are they three differennt diseases or simply different reactions to the same trauma.