Moyamoya disease is a chronic, occlusive cerebrovascular disease with unknown etiology, characterized by bilateral steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain . The association of moyamoya disease with further neurosurgical diseases, such as cerebral aneurysms [2-5], brain tumors, cervical carotid artery stenosis, and cerebrovascular malformations, has been described previously [6-11]. It is well known that moyamoya disease is frequently associated with intracranial aneurysms located within the abnormal basal network or the circle of Willis, which are explained by the intrinsic pathology of moyamoya disease, such as hemodynamic stress and fragile structure of the collateral vessels [2-5]. On the other hand, the association with atherosclerotic cervical carotid artery stenosis or with brain tumors leads to the diagnosis of akin moyamoya disease (quasi-moyamoya disease) according to the diagnostic criteria of the Research Committee on Spontaneous Occlusion of the Circle of Willis, of the Ministry of Health, Labor, and Welfare, Tokyo, Japan. The coincidence of moyamoya disease with cerebral vascular malformations including arteriovenous malformation [6, 7], cerebral cavernous malformation [8-10], and venous malformation  has been reported in the literature. A rare association of with dural arteriovenous fistula is also demonstrated . In this chapter, we especially focus on the association of moyamoya disease with further cerebrovascular disease based on our experience.
ASJC Scopus subject areas