Incidental major artery aneurysms in patients with non-hemorrhagic moyamoya disease.

Background: Major artery aneurysms may be found incidentally while evaluating moyamoya disease (MMD). The purpose of this study was to delineate the prevalence and characteristics of these uncommon aneurysms with a brief mention of their management and outcomes.
Methods: We conducted a retrospective review of 249 adult patients who were diagnosed with non-hemorrhagic MMD. Cerebral angiograms obtained at the time of initial diagnosis were carefully reviewed to identify incidental aneurysms located on a major intracranial artery or near its tributaries. Aneurysms originating from distal peripheral arteries or moyamoya vessels were ineligible for this study.
Results: Nine patients (3.6%) were found to have 13 major artery aneurysms, 7 (54%) of which were located in the posterior circulation, especially in older patients with bilateral MMD. The sizes of all aneurysms were less than 10 mm. Surgical clipping was performed on two aneurysms, and endovascular coiling on six (five posterior circulation aneurysms). Ischemic complications occurred in two patients after clipping of an anterior communicating artery aneurysm and in one patient after the second coiling of a recanalized basilar tip aneurysm.
Conclusions: Incidental major artery aneurysms can be found in 3.6% of adult patients with non-hemorrhagic MMD, an observed frequency that increases with age. About half of these aneurysms are located in the posterior circulation, particularly in older patients with bilateral MMD. Considering the risks of treatment-related complications, more information about the natural course of these aneurysms is needed to design proper management strategies both for the aneurysms and MMD.