Direct and In-direct By-pass
Cerebral artery bypass is utilized for mainly 4 categories: complex aneurysms that are not amenable to clipping or coiling, atherosclerotic narrowing of vessels leading to too little blood flow to the brain, Moyamoya disease, and tumor-invaded important vessels where blood flow to the brain needs to be maintained.
By-pass can be Direct or In-direct. Direct by-pass also known as extracranial-intracranial (EC-IC) bypass can provide blood flow to the anterior circulation of the brain (Carotid circulation) or the posterior circulation (Vetebrobasilar Circulation) of the brain.
Direct by-pass can be low-flow or high flow. Low flow grafts provide a flow rate of 15-25 ml/min, whereas high flow grafts provide a flow rate of 70-140 ml/min. Moderate to high flow grafts have a flow rate of 40-70 ml/min.