The prospects and pitfalls in the endovascular treatment of moyamoya disease-associated intracranial aneurysms.

Moyamoya disease (MMD) is characterized by progressive stenosis or occlusion of the distal internal carotid artery and simultaneous formation of collateral vasculature. The fragile alteration and increased hemodynamic stress in the intra- and extracranial vasculature would conjointly result in the formation of intracranial aneurysms in MMD patients. According to our classification, the MMD-associated aneurysms are divided into the major artery aneurysms (MAAs) and non-MAAs. The non-MAAs are further subdivided into the distal choroidal artery aneurysms, moyamoya vessel aneurysms, transdural collateral aneurysms, and anastomosis aneurysms. Currently, endovascular treatment (EVT) has become the main stream for the MMD-associated aneurysms. There is no difference to EVT for the MMD-associated MAAs of the non-stenosed major arteries with that in the non-MMD patients. While it is a big challenge to perform EVT for MMD-associated aneurysms in the stenosed arteries. Generally speaking, the parent arteries of the non-MAAs are slim, and super-selective catheterization is technically difficult. Most of the times, parent artery occlusion with liquid embolic agents or coils can only be performed. The vasculature in MMD patients is fragile; perioperative management and meticulous intraoperative manipulation are also very important to avoid complications during EVT. In spites of the complications, the EVT can bring good outcome in selected cases of MMD-associated aneurysms.