Purpose Strategies for treating intracranial aneurysms of collateral vessels in adult-onset moyamoya disease (MMD) remain unclear, because overall case numbers are limited and data on long-term outcomes are lacking. The aim of this study was to assess clinical and anatomic outcomes of such aneurysms in adult MMD sufferers who present with hemorrhage.

Methods Of the 77 adult patients consecutively enrolled between January, 2003 and December, 2014 in the MMD registry at a single institution, those presenting with hemorrhage and followed for >12 months were studied. Aneurysms involving collateral vessels at sites of hemorrhage were considered culprit lesions.

Results Aneurysms of collateral vessels in 19 patients (19/77, 24.7%) were confirmed as ruptured by conventional angiography. In five of these patients, obliterative endovascular embolization was successfully performed. The other 14 patients were managed conservatively due to lesion inaccessibility. Follow-up imaging studies (13 available) confirmed later disappearance of aneurysms in 12 patients (92.3%), although re-bleeding occurred in eight (42.1%) during follow-up (mean, 67.4 ± 38.9 months). The re-bleeding involved contralateral hemispheres in 6 patients (75.0%), and all re-bleeding events occurred >6 months after initial hemorrhages. In the other 58 subjects without aneurysm, 13 (22.4%) also suffered re-bleeding (mean follow-up, 71.9 ± 46.3 months).

Conclusion Although endovascular interventions are appropriate for ruptured aneurysms of collateral arteries in MMD, conservative treatment can be a viable alternative for technically inaccessible lesions. However, the re-bleeding rate in hemorrhagic MMD was higher in the presence of the aneurysms.

Disclosures Y. Cho: None. H. Kang: None. M. Han: None.