Dr. Frohman and Normal Pressure Hydrocephalus

A forum to discuss Chronic Cerebrospinal Venous Insufficiency and its relationship to Multiple Sclerosis.

Re: Dr. Frohman and Normal Pressure Hydrocephalus

Postby Rogan » Mon Oct 29, 2012 9:35 am

OneEye,
You are absolutely correct. My statement above that the brain is all liquid is just plain wrong. I think I got confused by reading about this from Wikipedia.

"Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior."

After a brief review of some very gross pictures on the internet of brain crashes, it is clear that the brain is liquid fluid and blood and spongy brain material. Sorry I was so wrong...Now, to some of your very interesting questions.

1eye wrote:What is the "normal" CSF pressure? How is it regulated?




Dr. Flanagan in his book "The Downside of Upright Posture" writes that

"Blood pressure in your arm is about 120 mmHg over 80 mmHg. That means that when the heart contracts, blood pressure rises to about 120 mmHg. In between beats, when the heart contracts, blood pressure rises to about 120 mmHg. In between beats, when the heart relaxes, it drops down to about 80 mmHg. That's fairly low, relatively speaking. While it takes a tight tourniquet to stop a bleeding artery, it only takes light finger pressure to compress a vein and stop blood flow. At about 10 to 20 mmHg, CSF and intraocular pressures are extremely low."

1eye wrote: Is there a good non-invasive way to measure instantaneous pressure? Seems to me ultrasound might accomplish this, if pressure affects the propagation of the sound waves. Would have to be a very sensitive and well calibrated instrument.


This is where Dr. Flanagan, again in the same book as some very interesting things to say. I am not done with the book, but he makes a strong point in arguing that glaucoma, may share the same disease process as NPH but it is with the eye, not the inner brain. His discussion that the eye is just an extension of the brain's third ventricle is fascinating. With this parallel in mind he goes on to write.

"Chronic glaucoma was once a major cause of degeneration of the optic nerve and subsequent blindness. It was difficult to detect and there were no treatments. Physicians had to rely on primitive spring gauges, called tonometers, which were pressed against the eyeball to check pressure. The spring gauges weren't that sensitive or accurate. Nowadays, fortunately, early detection has reduced the incidence of blindness due to glaucoma dramatically. Rather than spring gauges, today's eye doctors use computerized contact applanation and non-contact or air puff tonometry, as well as other highly sophisticated means, which are much more sensitive and accurate at detecting the extremely low pressures of glaucoma. When the condition is detected, drugs are now available that can decrease intraocular pressure and prevent blindness"

Perhaps some of these methods could be used to measure brain pressure? Or perhaps he discusses this later in his book, which I will post as I get there.
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Re: Dr. Frohman and Normal Pressure Hydrocephalus

Postby 1eye » Mon Oct 29, 2012 4:20 pm

Rogan:

I don't think you can measure pressure in the ventricles through the eyeball, but I could be wrong. There's no way to know, as far as I know. The idea of using sound waves is complicated by the bone, brains, arteries and veins around the ventricles. Sound does change its propagation speed with pressure, but this is too big of a science project for me.

Those Rochester NY folks have tracked CSF and found it follows incoming and outgoing blood vessels. That leads to the questions: what directs that flow, and also, what moves the CSF? I've seen different answers, from sodium pumps to convection.

What I would really like to learn is: what is the pressure normally, and how far is the normal deviation from that? Then it would be nice to see whether CCSVI/"MS" or Alzheimer's, or other degenerative brain diseases have abnormal pressures.

Venous pressure is far easier to measure: we can even do it with strain gauges on necks.
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Re: Dr. Frohman and Normal Pressure Hydrocephalus

Postby Rogan » Tue Oct 30, 2012 9:56 am

1eye wrote:
What I would really like to learn is: what is the pressure normally, and how far is the normal deviation from that? Then it would be nice to see whether CCSVI/"MS" or Alzheimer's, or other degenerative brain diseases have abnormal pressures.

It looks like from Wikipedia

http://en.wikipedia.org/wiki/Intracranial_pressure

"with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF"

"ICP is measured in millimeters of mercury (mmHg) and, at rest, is normally 7–15 mmHg for a supine adult, and becomes negative (averaging −10 mmHg) in the vertical position.[1] Changes in ICP are attributed to volume changes in one or more of the constituents contained in the cranium. Intracranial hypertension, commonly abbreviated IH, IICP or raised ICP, is elevation of the pressure in the cranium. ICP is normally 7–15 mm Hg; at 20–25 mm Hg, the upper limit of normal, treatment to reduce ICP may be needed"

The Monro-Kellie hypothesis, listed on the above link, is interesting in that it states that as lesions in the brain increase, the brain must compensate for them by lowering the amount of venous blood and CSF. This hypothesis may show why MS gets worse and worse as lesions grow. The brain would have even less venous blood in it?

Also Wikipedia lists a number of ways doctors can measure ICP, but the currently approved method sounds pretty invasive.

http://en.wikipedia.org/wiki/Non-invasive_intracranial_pressure_measurement_methods

Just as you suggested a couple of companies are working on non-invasive ways of measuring this.

Here's one http://www.fp7brainsafe.com/. As an interesting side note they look like they measure this by going through the eye. It looks like from reading the articles the doppler measurements aren't actuate enough yet. When these non-invasive tools are approved perhaps they could do a study as you suggest, looking at pwMS vs healthly controls. Sorry if all of this information has been posted before.
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Re: Dr. Frohman and Normal Pressure Hydrocephalus

Postby 1eye » Tue Oct 30, 2012 11:00 am

They know that because of individual differences, they have to have a calibration that is absolute, otherwise the doppler measurement is only relative. It's the calibration measurement that is invasive.

The device you pointed me to works probably in the same way as a blood-pressure cuff. It measures the pressure applied to the arm at the moment when blood movement stops. That balance point is said to correspond to the same amount of pressure the blood contains without the cuff.

So the optical artery has pressure applied to is until the simultaneous doppler device says that the movement of blood has stopped, and the applied pressure is said to correspond to the pressure from the brain side of the artery.

Do not be fooled. As in an electrical circuit, pressure drops occur every time a resistance of any kind is encountered. That means from the source, (the heart) all the way through the circuit.

If there were no difference between arterial and brain-arterial blood pressure, you could subtract the former (cuff) measurement from the eyeball-artery one, and say that the difference must be coming from the other sources in the brain (veins and CSF). If these measurements are normally always in the same ballpark, then the errors make no difference because everybody has roughly the same error. Maybe that's true.

Since the abnormal in veins and CSF is likely to be so close to the normal, in comparison to the much larger pressures seen in arteries, the size of error has to be much smaller as well.
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