Intracranial rebleeding in moyamoya disease

Abstract

Cerebral ischaemia and intracranial haemorrhage are the major catastrophic events in the natural course of moyamoya disease. To prevent cerebral ischaemia extracranial/intracranial (EC/IC) bypass surgery has been done and the results of the surgery have been well documented. However, the mechanism(s) underlying intracranial bleeding and the therapeutic modalities used to prevent bleeding have not been well elucidated. We have retrospectively analysed 45 cases with intracranial haemorrhage among 192 patients with moyamoya disease treated and followed at our institute. Analysis of the initial patients with haemorrhage did not provide any new information other than the already reported theories about the origin and mechanism of bleeding. Analysis of 15 patients in whom haemorrhage occurred at least twice suggested that there were two different mechanisms of rebleeding. One group consisted of 7 cases, where haemorrhages were confined to the original bleeding site. In 3 of these 7 cases a small aneurysm was identified at the periphery of a moyamoya vessel. In 1 case a ruptured aneurysm was found on a major vessel. In 3 other cases no source of bleeding was identified. In all but 1 of these cases rebleeding occurred within 2 months after the initial ictus. The second group consisted of 8 cases where haemorrhage occurred repeatedly but at variable sites. In none of these cases were aneurysms or other vascular abnormalities identified to suggest the source of bleeding and in all of these cases rebleeding occurred more than 2 months after the initial ictus. In moyamoya disease intracranial bleeding may occur as a result of rupture of a tiny aneurysm situated at the periphery of the moyamoya vessels and which may have been destroyed after the initial bleeding. If the aneurysms persist after rupture they may re-rupture after a fairly short interval. In other cases bleeding occurs at different sites from the initial haemorrhage; these are considered to be a result of rupture of weak moyamoya vessels which are forced to act as collateral pathways and are under unusually increased haemodynamic stress. EC/IC bypass surgery is considered to be effective for the prevention of rebleeding in both groups of patients but in selected cases. Direct surgery is recommended when a peripheral aneurysm is found on a moyamoya vessel which has bled once.