ICA–ECA collaterals

Knowledge and identification of multiple anastomotic connections between the external carotid artery and the internal carotid artery branches are paramount for the diagnosis and treatment of vascular diseases of the brain, head, neck, and spine. In this chapter, common extracranial–intracranial anastomoses of the ophthalmic artery, internal carotid artery, and of the posterior circulation that are critical for the proceduralist to recognize in order to avoid complications during embolization procedures or open surgery are reviewed. Finally, the role of noninvasive imaging in the evaluation of the collateral circulation and cerebrovascular reserve in clinical conditions associated with arterial occlusive disease is discussed.