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I have seen this happen in “normal pressure hydrocephalus- (NPH) Where there is a loss of gait, cognitive and bladder issues and the lesions disappear because the expanded ventricle swallows the lesion. I have shunted the brains of NPH patients, and they showed remarkable improvements. Again, the enlargement of the third ventricle precedes the changes.

The brain and spinal cord are surrounded by a clear fluid called cerebrospinal fluid (CSF). This fluid is produced and stored in cavities in the brain called ventricles. It circulates around the brain, moving from ventricle to ventricle. The purposes of the fluid are to cushion and protect the brain and spinal cord, to supply them with nutrients, and to remove some of their waste products. Any excess fluid drains away from the brain and is absorbed by other tissues.

Hydrocephalus is a condition in which there is too much CSF in the ventricles. This occurs when the natural system for draining and absorbing extra CSF does not work right. The ventricles enlarge to accommodate the extra fluid and then press on different parts of the brain, causing a number of different symptoms. Hydrocephalus has many different causes. Some people are born with the condition, while others develop it during their lives.

Normal pressure hydrocephalus (NPH) is a type of hydrocephalus that occurs in adults, usually older adults. The average age of people with NPH is older than 60 years. NPH is different than other types of hydrocephalus in that it develops slowly over time. The drainage of CSF is blocked gradually, and the excess fluid builds up slowly. The slow enlargement of the ventricles means that the fluid pressure in the brain may not be as high as in other types of hydrocephalus. However, the enlarged ventricles still press on the brain and can cause symptoms. (The term "normal pressure" is somewhat misleading.)

By definition, in secondary intracranial hypertension (SIH), there is an underlying medical condition, whereas in IIH, the cause is not known. In many cases of SIH, an increased cerebral venous pressure raises the intracranial pressure as in dural venous fistulas, venous sinus thrombosis, or venous sinus compression.1 However, in almost all patients with IIH (and also in our patients), neuroimaging shows narrowing of the transverse sinuses,2,3,5–7 not reflecting acute thrombosis. The important question is whether those venous abnormalities are cause or consequence of increased intracranial pressure. In the former situation, fixed stenoses (for example postthrombotic fibrotic changes) could obstruct the venous outflow, increase intracranial venous pressure proximal to the stenosis, and lead to increased CSF pressure as a result of a reduction in CSF absorption via the arachnoid granulations. In this setting, a pressure gradient across the stenosis should be measured and reconstruction of the venous lumen with endovascular stents would be effective in lowering elevated CSF pressure. This procedure was successfully used several times4,6 but seems not to be efficient in all patients.6 In the latter (ie, venous abnormalities as a consequence of intracranial pressure), elevated intracranial CSF pressure could lead to a secondary narrowing of the sinus lumen by compression, which can be reversed by lumbar puncture or shunt surgery procedures.5,7,8 In fixed stenoses (the 1st model), therapeutic reduction of CSF pressure should have no effect on sinus diameter.

How blood flow influences cerebrospinal fluid flow can be gauged from something called "cranial compliance", a measure of the elasticity of the brain's vascular system. "The cranium is a bony cavity of fixed volume, with the brain taking up most of the space," says Robin Kennett, a neurophysiologist from the Oxford Radcliffe Hospitals in the UK. "Every time the heart beats and sends blood into the cranium, something else has to come out to prevent the pressure rising to levels that would damage the brain." So, as fresh blood flows into the brain's blood vessels, cerebrospinal fluid flows out into the space around the spinal cord through a hole in the base of the skull called the foramen magnum.

Investigating Cerebral Circulation as the Physiological
Underpinning of Consciousness

A collaboration between the Beckley Foundation and the Sechenov Institute of Evolutionary Physiology and Biochemistry,
St. Petersburg, led by Prof. Yuri Moskalenko,
Amanda Feilding and Peter Halvorson

One of the projects we are most excited about at the Beckley Foundation is our collaboration with Prof. Yuri Moskalenko investigating cranial compliance. Cranial compliance is a measure of the functioning of the cranial system as a whole: the skull, the brain tissue, and all the liquids that flow through and around this complex system. Cranial compliance is determined by the interaction of all these components, and the results of our investigation so far have shown that a better understanding of these interactions is of crucial importance for healthier brains and improved cognitive functioning throughout the whole of one's life.

The Cranial System and Cranial Compliance

The circulation of blood in the brain differs from that of the other organs because the brain is encased within a nearly-rigid container, the cranium. The situation is further complicated by a second fluid system in the brain, the cerebrospinal fluid (CSF) system, which circulates in its own compartments and interacts with the blood system. These systems are interdependent such that changes in the volume, pressure and movements of one system should lead to concomitant changes in the other, consistent with the laws of fluid dynamics. The study of brain circulation has therefore evolved into the study of the bio-mechanical principles of how fluids move through soft tubes inside a closed container under pressure. There are many different configurations by which the two fluid volumes interact, and learning more about these reveals vital new information about brain circulation and its implications for health.

The concept of brain circulation from this systemic point of view, as a complex biological system, has been given the name cranial compliance or CC. Understanding CC is relevant to medical professionals as well as for each and every one of us. Changes in the elasticity of this complex system over the life span have been shown to have a direct impact on cerebral health and cognitive functioning, as our most recently completed research clearly demonstrates. To know and to manage cranial compliance is as important for the good health of the brain as knowing and managing one's blood pressure is for the heart. The good news is that our research indicates that early, proactive management of cranial compliance may counteract the diminution in brain functions considered to be an inevitable part of normal ageing.

The importance of good cerebral circulation and our intuitive understanding of this is highlighted by the long history we humans have of devising practices that improve our cerebral circulation. The benefits of yogic breathing exercises to cranial compliance, for example, indicate an appreciation that inspiration and expiration (i.e. respiratory pressure changes) are one of the driving forces of brain circulation. Indeed, the respiratory system can be considered as a third fluid system in terms of the effects it has on blood and CSF movements. Altering the extent and rhythm of breathing influences the quality and quantity of fluid movements around the brain.

As described above, to really understand cranial compliance and cerebral circulation you have to consider the brain and the cranial system as a holistic whole. The complex cranial structures that influence brain circulation are:-

1) the skull and it's membranes; 2) the vessels and their blood content; 3) the brain tissue; and 4) the cerebrospinal fluid system within all of its various compartments and convolutions. The CSF system cushions the brain and is, most importantly, responsible for the cleansing of the tissue, like a special lymphatic system just for the brain that can remove waste products too large to pass back into the blood stream.

But I thought I understood Mark's new stenosis is low down in the jugs not in the sinus If all secondary stenoses end up in the sinus that may be at issue but so far has anyone had a sinus stenosis after the fact?

I think I remember one person had one in the first place, isn't that interesting to think about, a stenosis that increases venous pressure... but also results in intracranial pressure on the sinus after the fact as well? A double whammy! Wow, what a neat thing we can get treatment

There is a fly in the ointment though: MSers do not have intracranial hypertension if we did, that would be noted in all of us when we got our testing. A lumbar puncture would show it. Normal pressure hydrocephalus is a little different in that it is not a high pressure deal, even though it presses on tissue, it is a mild press. The similarities between the CCSVI and NPH have to do with the low pressure situation....but still pressure.

I am not sure that even though stenosis of the sinus can happen in the SIH situation you can extrapolate and say that it also can do that in NPH.....
marie

In particular if it's in the neck, why would that external pressure change for good at some point in somebody's live?