Andrew, Norwich asked:
I was just wondering if you know what the mechanism is that controls your CSF pressure?
Chris - Your brain and spinal cord sit inside your skull and the cavity that runs down inside your spinal column, and they're invested in some layers called the meninges which wrap up the brain and spinal cord. Inside those layers is a fluid called cerebrospinal fluid, and the brain bops around in that fluid. It effectively acts as a cushion to support the tissue because the nerves in the brain are very delicate and they need that additional cushioning support.
The cerebrospinal fluid is actually made right inside the brain. You have a network of blood vessels called the choroid plexus and those blood vessels work rather like a coffee filter. The blood goes through them and the walls are slightly leaky, so liquid, but not cells, comes out of the blood and goes inside some holes in the brain called ventricles. This liquid flows out of those ventricles and then out into the space around the brain. Right at the top of your head, between the two hemispheres is a structure called the falx cerebri and in there is a very large blood vessel called the sagittal sinus. The dura, which is one of the layers of the meninges, makes that special blood vessel and itís perforated in various places by these structures called arachnoid granulations. These are little pouchings, that are mushroom shaped, of the additional layer around the brain, the arachnoid layer around the brain, and the CSF goes up into those little mushroom-shaped bodies, and is re-absorbed into the blood stream via that route. So blood comes out of the middle of the brain, goes around the brain, and then is re-absorbed into this big blood vessel that runs from front to back in the middle of your head. The reason that the pressure can go up is if those arachnoid granulations get blocked or if that big blood vessel, the sagittal sinus, gets blocked and sometimes if too much CSF is produced as well for whatever reason.
You can lower the pressure by treating the underlying condition whatever has caused the obstruction, or by reducing the formation of the cerebrospinal fluid in the first place. And one way to do that is to give a drug called a carbonic anhydrase inhibitor. I think one of those is a drug called acetazolamide and this will reduce the rate at which CSF is being formed and therefore, the CSF pressure drops a little bit.