The Paramount Role of the Anterior Communicating Artery in the Collateral Cerebral Circulation.

Clinical manifestation of carotid occlusive disease is largely dependent on the severity of stenosis and the capability of collateral circulation. However, due to the complexity and difficulty in evaluation, cerebral collateral circulation has, so far, remained underappreciated. We report a patient with advanced extracranial arterial disease (including the right subclavian steal, occlusion of the right external carotid artery, and severe stenosis of the left vertebral artery), who underwent transient right internal carotid artery occlusion during carotid intervention. Throughout the occlusion, the flow into the right hemisphere (monitored by transcranial Doppler ultrasound in the right middle cerebral artery) was sufficient despite almost totally dependent on the anterior communicating artery, which highlights its role as the most potent collateral pathway.