Andy, I'm sure it's an in depth topic amongst specialists. Since coming to work at a hospital that is the go to place for this type of thing in the Pacific Northwest, I have gained a great deal of respect for this short artery and I consider it the "blue wire" the Circle of Willis. It's more than just a conduit to the COW. Its branches feed our lizard brain (respiration, circulation). I know that if collaterals are robust, it can be sacrificed to eliminate an aneurysm. Our neurosurgeons will bypass from the CCA to the PCA to augment perfusion in some circumstances. I will see what I can dig up for you.