Cervico-cephalic arterial thrombi and thromboemboli in moyamoya disease--possible correlation with progressive intimal thickening in the intracranial major arteries.

Ninety-two thrombi and/or thromboemboli of cervico-cephalic arteries were confirmed histopathologically in 16 out of 22 patients with moyamoya disease. Included were 74 white thrombi mainly composed of fibrin and platelets, 9 organized thrombi and 9 mixed thrombi containing red blood cells. Thirteen microthrombi and one organized thrombus were located in the cervical arteries. Seventy-eight thrombi were present in the intracranial major arteries. Sixty-five were white microthrombi attached to the luminal surface of the arteries. The intracranial microthrombi were most frequently observed at the distal ends of the internal carotid arteries (29 thrombi). The fibrous thickening of the intima and edema in the innermost luminal surface were the most common vascular alterations associated with the thrombus formation. In two patients, thrombus formation was associated with fissure of the thickened intima and a dissecting aneurysm. We concluded that in patients with moyamoya disease the thrombi may be closely related to the development of intimal thickening in the intracranial arteries, particularly at the distal ends of the internal carotid arteries.