I have been wondering about this and can't find any information about it.  From what I understand, the puff of smoke blood vessels are dangerous because they are so small and weak and are prone to hemorrhage.  After my son gets the surgery done and new vessels grow then what happens to those dangerous ones?

Thanks.

Lynn, I have always wondered the same thing and still don't have an answer.  Maybe we'll get one soon.

Hi Lynn,

I'm not a doctor but in lay terms, this is how I understand the collateral vessels (puff of smoke).

Everyone has collateral vessels. The collateral vessels normally aren't open. However, with MM the collateral vessels grow and enlarge and therefore open to supply blood and oxygen due to the blockage in the artery. I also read that collateral vessels don't open in all people.

My understanding is that the collateral vessels are always present but they might not be open. So after by-pass surgery, the collateral vessels are still present but not necessarily open or functioning in terms of supplying blood and oxygen.


Lore

I'm not a doctor either but I am currently studying nursing and plan to go on to medicine afterwards.

I agree with Lore, with a bit of an extension:

The danger with the collateral blood vessels is that when they open up due to the narrowing of the larger arteries, they create a detour around the narrow/blocked artery and can end up being the sole supply of blood and oxygen. Because they are so small compared to the volume of blood flow, they can be prone to hemorrhages.
After surgery, the new arteries (or blood vessels, depending on the nature of the bypass) are larger and stronger than these collateral vessels and more capable of delivering the required blood flow.

My understanding is that the collateral blood vessels would generally still remain open and just help out in getting all the blood to where it needs to go. Because they aren't the sole mode of transport, the risk of them hemorrhaging is significantly decreased.

I hope this helps a bit.

Here is what I was told when my son had his surgery almost twelve years ago.

The "puff" vessels are caused because the major artery is closing.  These puff vessels are dangerous because they are so small.  The smallest clot can hit them (or the narrowed part of the major artery) and cause a stroke OR it can cause a bleed -- which is supposed to more common in adults. 

If you look at the arteriogram, you will see that the "puff" vessels all form above the narrowing of the major artery.  Once the major artery completely closes, the puff vessels will no longer receive blood.  As a result, they wither and are no longer visible on an arteriogram.  Basically, they deteriorate just as the top portion of the closed artery did. 

Kim -- mom to Matthew, 19, 3 strokes at 7 due to moyamoya and single left kidney due to moyamoya causing renal artery stenosis