Dr. Tai at ISNVD

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

Dr. Tai at ISNVD

Postby Cece » Sat Feb 25, 2012 6:35 pm

page 69 http://www.isnvd.org/files/ISNVD%20Abstract%20Book.pdf
Measurement of Azygos Venous Blood Flow in Patients with
Multiple Sclerosis Using MRI
MRI is an effective non-invasive method of measuring the rate of blood flow through the azygos veins in the MS population. The azygos blood flow in patients with multiple sclerosis was similar to controls in this study, as seen by performing t-test analysis on the two sets of data resulting in a p-value greater than 0.05, indicating that the two means are statistically equal. No significant differences in blood flow through the azygos vein were observed between the three types of MS patients (p >0.05).
We don't know if this means that the MS population is indeed equal to the healthy controls in terms of blood flow in the azygous vein or if it means that MRI is not effective at measuring blood flow in the azygous vein, and in particular the flow abnormalities due to CCSVI intraluminal abnormalities. Dr. Fox's Cleveland Clinic autopsy study included azygous veins in the autopsied veins that were studied, and intraluminal abnormalities were observed in MS patients, so I tend to suspect that the blood flow is impaired in the azygous vein in a subset of MS patients and that the MRI of the azygous was not sensitive enough to pick this up.
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Re: Dr. Tai at ISNVD

Postby Brainteaser » Sat Feb 25, 2012 8:56 pm

Cece,
I sometimes wonder how much flawed logic there is in the medical community, when as in situations like this, it takes you as a lay person, to see the methodological problem.
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Re: Dr. Tai at ISNVD

Postby klr290 » Tue Feb 28, 2012 8:30 am

I believe it's true that you cannot use this study to make a confident claim that azygos blood flow is equal between MS patients and healthy controls; however, you cannot also assume that Dr. Tai is making that claim. She performed a study and published the results. That's all. If she came out and said, "therefor, this study proves...", then yeah I would say that is some false logic...

So sure, maybe we will eventually find that there are different types of MS and that average azygos flow is different in only one of the types (like what cece said about a subset). Or it could also be possible that azygos blood flow may still be abnormal even with a normal looking average flow, because that is all they compared. Who knows? There is still a lot of research to be done.
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Re: Dr. Tai at ISNVD

Postby Cece » Tue Feb 28, 2012 9:24 am

So much research to be done! I agree. And welcome to TiMS.

It is discouraging if the MRI turns out not to be sensitive enough to pick up azygous abnormalities, because there is no noninvasive way to directly image the azygous other than MRI. The conclusions possible from this research are either that the sample size was too small to show the differences, or there are no differences between the azygous flow in MS patients as compared to healthy controls, or that MRI is not sensitive enough to pick up the differences, particularly if it's a matter of intraluminal abnormalities. I agree that Dr. Tai made no claims beyond what is in the paper itself. I should double-check too; I assumed this was MRV with TOF or TRICKS or whatever it is that sets the Haacke-protocol MRVs different from regular MRVs (with the Haacke MRVs more capable of looking at flow than a traditional MRV.)

From the clinicians who are treating CCSVI, and particularly those who are using IVUS, I believe azygous abnormalities are present in pwMS in about a quarter of patients. Are they present in a quarter of healthy controls? We aren't going to be getting IVUS data on healthy controls anytime soon.
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Re: Dr. Tai at ISNVD

Postby klr290 » Tue Feb 28, 2012 2:12 pm

I agree it would be discouraging. Hopefully technical advances in MRI will soon eliminate any flow sensitivity issues. Also, yes, I think sample size was probably an issue; especially with the control group.
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Re: Dr. Tai at ISNVD

Postby mimi6565 » Fri Mar 02, 2012 2:28 pm

Important :

"No distributional differences in the azygous flow does not mean there are not problems.

To understand this consider the following: if you pinch a tube even to 50% there will be narrowing but the flow will be the same. So it is not just flow that is key but in this case also cross sectional measurements. Here there were some cases that showed narrowing in the azygous and there has even been a case where the azygous flow stops (but not in that abstract).

The key is to understand the physics so the scientists really do know what they are doing here but one must also be aware of statistics, properly understanding both flow and cross sectional area, etc." ( from an expert at the ISNVD meeting)

They did find that there were more narrowings in the MS population and that was presented at the ISNVD/
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Re: Dr. Tai at ISNVD

Postby Cece » Fri Mar 02, 2012 5:24 pm

Average azygos venous blood flow in the MS population was found to be 2.87
ml/sec (SD = 1.27) at the upper level and 2.01 ml/sec (SD=1.3) at lower level.
Controls had at the upper level an average blood flow of 2.51 ml/sec (SD = 1.24)
in the azygos vein which is similar to those seen in previous studies [4,5].
Patients with RR-MS had an average blood flow of 2.97 ml/sec, SP-MS blood flow
average 2.65 ml/sec and PP-MS average blood flow of 2.76 ml/sec.
It is interesting that in the MS patients, the azygous flow was higher in the upper azygous by the arch and lower at the lower level. I wonder if that is a normal occurrence in the controls as well or if that could be indicative of a slowing down of the flow as it passes through the azygous in the MS patients? But not statistically significant.

It would be helpful to be able to sort out the MS patients with confirmed azygous stenoses (as found during angiography) from those without it. Clinics such as Dr. Ponec's and Dr. Arata's, that are doing pre-procedure MRIs, must have the data to work with. Perhaps we'll see it presented at next year's ISNVD! Then the MS patients with known azygous disease could be compared to the healthy controls, and maybe then any difference would be more pronounced.

Let me look at this:
Blood flow was measured at two levels in the
azygos: one at the upper level immediately below the arch and the other at a lower
level.
Azygous stenoses are often found in the arch. I wonder if the flow measurement could have been taken at the peak of the arch, and if that would have impacted the findings?

I am a layman, and this is difficult material to work through. I hope not to misrepresent anything.

For the pinching tube analogy, if the flow is the same even when pinched, that begs the question of if it is structure that matters or if it is the flow that matters. Does a structural abnormality in the absence of a flow abnormality have an effect, and would treating it change anything?

My own azygous was extra-large with rapid flow. Dr. Sclafani's assessment was that it was taking flow that was coming down the vertebral veins and vertebral plexus instead of being able to travel down the jugulars, which were nearly entirely blocked. Perhaps I would have been discarded as an outlier, if my MRIs had been in this study.

One of the questions raised in this thread was whether or not the MRI is an effective method of measuring the rate of blood flow through the azygos veins, as stated in the first line of the conclusions of Dr. Tai's research. The azygous is a small vein, and there must be an effect from mediastinal movement, even if shielding is used? I am checking google scholar. It is as always an understudied vein.
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Re: Dr. Tai at ISNVD

Postby mimi6565 » Sun Mar 04, 2012 12:38 pm

I love your questions. I encourage you to continue challenging the experts .
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Re: Dr. Tai at ISNVD

Postby Cece » Sun Mar 04, 2012 1:50 pm

Thanks, Mimi.
klr290 wrote:Or it could also be possible that azygos blood flow may still be abnormal even with a normal looking average flow, because that is all they compared.
There was the research from Dr. Siddiqui, looking at the azygous with ivus. chronic-cerebrospinal-venous-insufficiency-ccsvi-f40/topic19274.html#p186864
The most common finding in that study using intravascular ultrasound in the azygous was reduced pulsatility. That is a new and potentially interesting concept in CCSVI. The next most common findings were stenosis and intraluminal abnormalities. I wonder if reduced pulsatility of the azygous can be measured by MRI.

I only did a partial search of google scholar for information about the use of MRI in the azygous in other diseases. MRI of the azygous vein was used in people with portal hypertension that redirects flow to the azygous. A difference was seen from before compared with after shunt placement (that allowed blood to flow properly and not be redirected to the azygous). That study had a small sample size of 20. It might be easier to tease out that improvement as statistically significant in that study since the flow situation was acute, as opposed to the potentially less acute but more chronic effect of azygous blockages causing reflux in CCSVI patients. Also the portal hypertension would only affect the azgyous flow in one way (increasing flow) whereas CCSVI might cause increased flow or reflux or slowed flow, depending on the locations of stenoses. In an additional subset of CCSVI patients, a renal stenosis may be redirecting flow to the azygous as well. CCSVI is nothing if not varied.
http://onlinelibrary.wiley.com/doi/10.1 ... 2/abstract

Brainteaser, I don't think there is a methodological problem. The conclusions were not as definitive as I'd like. In an ideal world, all research would involve multimodal imaging (MRI + doppler+ flouroscopy + ivus) and be large-scale research and the results would be as definitive as the trial design allowed. This is more modest research. I am waiting for the critical tipping point for CCSVI, when it becomes clear to everyone that this is the right track, and the funding comes pouring in.

Such a fascinating topic! I'd had an MRI of my azygous back in 2010, prior to being treated, that led me to believe I'd have an azygous stenosis, but none was to be found, not even with IVUS.
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Re: Dr. Tai at ISNVD

Postby 1eye » Sun Mar 04, 2012 4:06 pm

Narrowness can be without any change in CSA (the pinching example), or where the entire circumference is reduced, where flow would also be reduced. That would be more likely at a valve, I think. At some point the shape of the tube might matter; not sure of the physics, but the cross sectional shape may change with gravity because the vessels have soft walls and low pressure. Maybe the effect of intraluminal thingies is more or less pronounced in different postures.
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