2018 Volume 27 Issue 7 Pages 522-527
As a result of the recent advances in research of moyamoya disease, diagnostic criteria in Japan were revised in 2015. Several studies have proved that direct extracranial-intracranial (EC-IC) bypass plays essential role not only for reduction of ischemic stroke, but also of rebleeding risks in adult patients. Subanalysis of Japan Adult Moyamoya Trial indicates that patients with bleeding in the posterior circulation territory are particularly at higher risk of rebleeding and obtain greater benefits from a direct EC-IC bypass. However, some topics related to direct EC-IC bypass for patients of moyamoya disease remain still unsolved. It is difficult to distinguish the presence of intracranial arteriosclerosis in some patients of supposed moyamoya disease unless RNF213 is clarified as a susceptibility gene. The surgical management in patients of rapidly progressing moyamoya disease who suffer from repeated ischemic stroke in a short period of time remains unsolved. Direct EC-IC bypass provably allows to prevent aggravating ischemic stroke, however perioperative ischemic complications cannot be ignored and best treatment including direct EC-IC bypass cannot completely prevent ischemic stroke, especially in some young pediatric patients. Hyperperfusion has been reported to be one of the essential phenomena which causes focal intracranial hemorrhage or some other postoperative complications. Recently some specific radiographical changings after direct EC-IC bypass in patients of moyamoya disease, such as vasogenic edema, high intensity in the sulcus on fluid-attenuated inversion recovery (FLAIR) images, and subcortical low intensity on FLAIR images have been reported. These radiographical changes appear within several days after operation with or without transient neurologic events and disappear within several weeks. The mechanism of these findings and their relationship to postoperative complications such as transient neurologic events, ischemic stroke, and focal intracerebral hemorrhage remains unclear. A future study of cognitive impairment in patients of moyamoya disease and effectiveness of direct EC-IC bypass to improve it should be conducted. After an accurate evaluation of cognitive impairment including radiographical findings in patients of moyamoya disease, appropriate indication of direct EC-IC bypass to improve that deficit may be established. A future study of the natural history of asymptomatic moyamoya disease will also be of value to clarify indications of direct EC-IC bypass.
