Endovascular management of a collateral network aneurysm in a patient with spontaneous internal carotid artery occlusion.

Spontaneous "non-moyamoya" arterial occlusion of the intracranial arteries is very unusual. Progressive occlusion of a major intracranial artery, independently from the etiology, can lead to the development of collateral arterial networks that supply blood flow to distal territories beyond the occlusion. These collateral arteries are typically small and conduct low flows, but the hemodynamic stress within them can lead to aneurysm formation within the collateral network. In this report we present a case of spontaneous internal carotid artery occlusion and collateral network aneurysm for the first time in the literature and discuss the main features of the etiology and endovascular treatment of this rare, challenging aneurysm.