Recurrent bleedings have been known to aggravate the prognoses of patients who experienced cerebral bleeding attacks related to moyamoya disease. Hemodynamic stress on the moyamoya vessels enlarged as collateral pathways has been attributed to the bleeding episodes. Bypass surgery has been performed for these patients to prevent recurrent attacks by reducing the hemodynamic stress on the moyamoya vessels. However, the preventive effect of bypass surgery against recurrent bleedings has not yet been statistically proven.
To establish the treatment guidlines for moyamoya disease with hemorrhagic onset, 20 Japanese centers have combined to evaluate the benefit of direct anastomotic bypass surgery such as superficial temporal artery to middle cerebral artery anastomosis in randomized patients who have experienced hemorrhagic episodes related to moyamoya disease and who have received either best medical treatment alone or best medical treatment plus extracranial-intracranial bypass surgery. This prospective randomized controlled trial named the Japan Adult Moyamoya (JAM) Trial was initiated in January 2001. Twenty patients have been already enrolled in this study.