Why do doctors wait for brain aneurysms to grow a little larger before surgery or coiling?

Instead of removing it while it is still small?

[Eddie1994]

The aneruysm is never removed.  It is either clipped, stented, glued, or coiled.  Some aneruysms don't grow beyond a certain size.  Others may continue to grow larger or wider.  Waiting until it grows to a certain size allows the Doctor to determine the optimal procedure.  As I understand, 5.0 (cm or mm, can't remember which) is the size that warrants intervention.  Growing from a 3.5 to a 4.0 could take years or months - no knows for sure.  

[Starshine1215]

In my case, my aneurysm was so small (I think about 3mm), the doc had trouble getting the coil in it. He was able to do that after some work, and it did start to clot out which is the goal.  Probably hours to a couple of weeks later, the coil migrated to another artery where it has adhered to the wall.

So, now, we're just going to wait and see.  I'll have another angiogram or MRI (I forget.  Eddie1994?) in a year.