INTRACRANIAL REBLEEDING IN MOYAMOYA DISEASE

Cerebral ischaemia and intracranial haemorrhage are the major catastro phic events in the natural course of moyamoya disease. To prevent cere bral ischaemia extracranial/intracranial (EC/IC) bypass surgery has be en done and the results of the surgery have been well documented. Howe ver, the mechanism(s) underlying intracranial bleeding and the therape utic modalities used to prevent bleeding have not been well elucidated . We have retrospectively analysed 45 cases with intracranial haemorrh age among 192 patients with moyamoya disease treated and followed at o ur institute. Analysis of the initial patients with haemorrhage did no t provide any new information other than the already reported theories about the origin and mechanism of bleeding. Analysis of 15 patients i n whom haemorrhage occurred at least twice suggested that there were t wo 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 v essel. In 3 other cases no source of bleeding was identified. In all b ut 1 of these cases rebleeding occurred within 2 months after the init ial ictus. The second group consisted of 8 cases where haemorrhage occ urred repeatedly but at variable sites. In none of these cases were an eurysms or other vascular abnormalities identified to suggest the sour ce of bleeding and in all of these cases rebleeding occurred more than 2 months after the initial ictus. In moyamoya disease intracranial bl eeding may occur as a result of rupture of a tiny aneurysm situated at the periphery of the moyamoya vessels and which may have been destroy ed after the initial bleeding. If the aneurysms persist after rupture they may re-rupture after a fairly short interval. In other cases blee ding occurs at different sites from the initial haemorrhage; these are considered to be a result of rupture of weak moyamoya vessels which a re forced to act as collateral pathways and are under unusually increa sed haemodynamic stress. EC/IC bypass surgery is considered to be effe ctive for the prevention of rebleeding in both groups of patients but in selected cases. Direct surgery is recommended when a peripheral ane urysm is found on a moyamoya vessel which has bled once.