In this report, we, the Research Committee on Moyamoya Disease (Spontaneous Occlusion of the circle of Willis), describe in detail the changes in the new "Diagnostic Criteria 2021" for moyamoya disease and its scientific basis to make it widely known to the world. The revised criteria cover all aspects of the disease, including a definition of the disease concept, diagnostic imaging, and the concept of quasi-moyamoya disease (moyamoya syndrome).

Background and Purpose— The progression of occlusive lesions in the major intracranial arteries was believed to be very rare in adult patients with moyamoya disease. The present study aims to clarify the incidence and clinical features of disease progression in adult moyamoya disease. Methods— For the past 15 years, 120 adult Japanese patients were diagnosed with moyamoya disease. Of these, 63 patients were enrolled in this historical prospective cohort study on a total of 86 nonoperated hemispheres. All were followed up with a mean period of 73.6 months. MRI and magnetic resonance angiography were repeated every 6 to 12 months, and cerebral angiography was performed when disease progression was suspected on MRI and magnetic resonance angiography. Results— Disease progression occurred in 15 of 86 nonoperated hemispheres (17.4% per hemisphere) or in 15 of 63 patients (23.8% per patient) during the follow-up period. Occlusive arterial lesions progressed in both anterior and posterior circulations, in both symptomatic and asymptomatic patients, and in both bilateral and unilateral types. Eight of 15 patients developed ischemic or hemorrhagic events in relation to disease progression. Multivariate analysis revealed that the odds ratio conferred by a male patient was 0.20 (95% CI, 0.04 to 0.97). Conclusions— The incidence of disease progression in adult moyamoya disease is much higher than recognized before, and female patients may be at higher risk for it than male patients. Careful follow-up would be essential to prevent additional stroke occurrence in medically treated adult patients with moyamoya disease, even if they are asymptomatic or are diagnosed as having unilateral moyamoya disease.

Background and Purpose— Although the development of a noninvasive MR examination has increased the opportunity to identify asymptomatic patients with moyamoya disease who have experienced no stroke episodes, their clinical features are still unclear. This was the first multicenter, nation-wide survey focused on asymptomatic moyamoya disease in Japan and was designed to clarify their clinical features. Methods— A clinical database of asymptomatic patients with moyamoya disease was collected from 12 participating hospitals in Japan between 2003 and 2006. In total, 40 patients were enrolled in this historical prospective cohort study. Of these, 6 underwent surgical revascularization, including superficial temporal artery to middle cerebral artery anastomosis and/or pial synangiosis. Their demographic and radiological findings as well as outcome were evaluated. Results— On initial evaluation, cerebral infarction and disturbed cerebral hemodynamics were detected in ≈20% and 40% of the involved hemispheres, respectively. Angiographical stage was more advanced in more elderly patients. Of 34 nonsurgically treated patients, 7 experienced transient ischemic attack (n=3), ischemic stroke (n=1), or intracranial bleeding (n=3) during follow-up periods (mean, 43.7 months). The annual risk for any stroke was 3.2%. Disease progression was associated with ischemic events or silent infarction in 4 of 5 patients. No cerebrovascular event occurred in the 6 patients who underwent surgical revascularization. Conclusions— The findings revealed that asymptomatic moyamoya disease is not a silent disorder and may potentially cause ischemic or hemorrhagic stroke. Asymptomatic patients with moyamoya disease should be carefully followed-up to further clarify their outcome and to establish the management guideline for them.

Despite recent developments in innovative treatment strategies, stroke remains one of the leading causes of death and disability worldwide. Stem cell therapy is currently attracting much attention due to its potential for exerting significant therapeutic effects on stroke patients. Various types of cells, including bone marrow mononuclear cells, bone marrow/adipose-derived stem/stromal cells, umbilical cord blood cells, neural stem cells, and olfactory ensheathing cells have enhanced neurological outcomes in animal stroke models. These stem cells have also been tested via clinical trials involving stroke patients. In this article, the authors review potential molecular mechanisms underlying neural recovery associated with stem cell treatment, as well as recent advances in stem cell therapy, with particular reference to clinical trials and future prospects for such therapy in treating stroke.