MECHANISM OF INTRACRANIAL REBLEEDING IN MOYAMOYA-DISEASE

Intracranial hemorrhage is the major catastrophic event in the natural course of Moyamoya disease, and outcome of the patients with rebleedi ng is very poor. However, the mechanism underlying intracranial reblee ding is not well elucidated. We retrospectively analyzed 15 patients w ho bled two times or more among 46 bled patients with Moyamoya disease . The results indicated that there were two different types in the man ner of rebleeding. One group consisted of seven cases, which bled two times or more at the same site than the original bleeding site. In fou r of these seven cases, a ruptured aneurysm was identified at the dist al part of collateral vessel or on the major vessel. In the other thre e cases, no source of bleeding was identified. In all of these cases, rebleeding occurred within 2 months after the initial insult except fo r one case. Another group consisted of eight cases, which bled repeate dly but at different sites from the initial bleeding site. In any of t hese cases, neither aneurysms nor other vascular abnormalities were id entified. In all of these cases, rebleeding occurred more than 2 month s after the initial bleeding. The present result indicated that intrac ranial bleeding might occur as a result of rupture of a tiny aneurysm at the periphery of collateral vessels. These aneurysms may be blown o ut after the initial bleeding. When they persist after the event, they may rupture again in a fairly short interval. In other cases, bleedin g occur at different sites from the initial site. They are considered to be a result of ruptured weak Moyamoya vessels which are forced to a ct as collateral pathways and are under unusually increased hemodynami c stress. (C) 1997 Elsevier Science B.V.