An extracranial-intracranial bypass is a technique used to augment the blood flow to the brain. The common carotid artery is located in the neck and supplies blood to the brain, face, and scalp. At the jaw the common carotid artery divides into the internal carotid artery that supplies blood to the brain and the external carotid artery that carries blood to the face and scalp. When the internal carotid artery is unable to carry enough blood to the brain, blood may be diverted from the external carotid artery to supply the brain by means of a bypass. The blood may be diverted from the external carotid artery to the blood vessels in the brain by using a vein graft or an arterial graft to join the two circulations.
Why Would Someone Need an Extracranial-Intracranial Bypass?
An extracranial-intracranial bypass is used to treat a select group of patients. Some patients who have experienced strokes attributed to poor cerebral blood flow (cerebral hypoperfusion) may benefit from a bypass procedure. Other patients with complex vascular conditions requiring closure of the carotid artery may need a bypass procedure as well.
A) Pre-operative lateral angiogram demonstrating occlusion of the supraclinoidal segment of the internal carotid artery.
B) Post-operative 3-D reconstruction of a CT angiogram demonstrating a patent bypass graft. In this case the bypass graft is the superficial temporal artery (STA), and it is joined to the middle cerebral artery (MCA), restoring blood flow to the brain. This type of bypass is called a STA-MCA bypass.
C) Post-operative coronal CT angiogram demonstrating the patent bypass graft and the revascularized middle cerebral artery territory (arrowheads).