The evidence-based practice guidelines for moyamoya disease (MMD) proposed by Drs. Smith and Scott,1 who are world-leading scholars in the field, are a wellsummarized reference for doctors managing the treatment of patients with MMD, especially in areas in which MMD is not prevalent. These investigators have created a framework that can be modified as knowledge and experience are accumulated in the field of basic research as well as clinical practice. Among many pertinent issues, I would like to comment on some points of controversy and future directions. The differential diagnosis of MMD should be made cautiously, especially in areas in which this disorder is rather common. Some of the vascular inflammatory diseases or intracranial arteriopathy may mimic the clinical features of MMD. In Asian countries, unilateral stenosis of the middle cerebral artery with faint collateral channels at the base of the brain is common. Occlusion of the M1 portion with basal ganglia infarction seems to be a different entity, with spontaneous improvement and no progression of disease as is observed in MMD. Moyamoya disease progresses rapidly in children younger than 3 years. It frequently manifests with stroke, without preceding transient ischemic symptoms. These patients are prone to bilateral widespread infarction if management is delayed. In these cases, screening is an important issue. Unfortunately, however, although MMD shows genetic and racial predisposition, genetic screening is still not possible. Screening with MRI studies for family members of patients with MMD may be helpful. Nonetheless, the rate of progression in young children is so fast that a single MRI examination cannot predict the occurrence of disease during the period of high-risk, MMD-induced wide infarction. Genetic and molecular research will be crucial for the protection of these young children. The management of ischemia in children with MMD by revascularization surgery, whether it is direct, indirect, or combined, cannot be investigated by a randomized clinical trial because this approach would be unethical. On the other hand, surgery has not been widely accepted in cases with bleeding, due to the lack of solid evidence. There are controversies regarding the use of aspirin or anticoagulation therapy, except with respect to perioperative use for direct revascularization surgery. The main primary pathology, fibromuscular intimal hyperplasia, also raises questions about the long-term use of aspirin or anticoagulation therapy. Keeping physiological factors such as body temperature, circulation volume, hemoglobin level, and blood levels of O2 and CO2 within the safe ranges is most important to avoid perioperative ischemic complications. Anesthesia with hyperventilation, as is preferred in most brain operations, is highly dangerous in MMD, but this caveat is sometimes neglected in the institutes in which MMD operations are seldom performed. Postoperative crying and agitation should be controlled. The scalp tissue in children is thin, and the wellvascularized layers are detached and inserted into the intracranial cavity in indirect revascularization surgery. The remaining, less vascularized thin layers with defective underlying tissue are vulnerable to necrosis. Great care should be taken when handling scalp tissue in young children. Improvement of the ischemic symptoms is rapid, and it occurs not in a matter of months, but rather of weeks. The duration of the hospital stay or perioperative treatment with hydration, anticonvulsants, and so on should be decided based on the usual and unusual early postoperative course of MMD. Postoperative headache or ischemic symptoms are not rare. Although the revascularization surgery improves the hemodynamic status of the brain, it does not halt the progression of MMD itself. The progression of arterial stenosis may lead to the progressive dilation of collateral channels and may cause headache. The headache has several characteristics. A bothersome headache can be relieved by additional revascularization surgery. Young patients or patients with long-term follow-up often exhibit recurrent ischemic symptoms or infarction. Protocols for long-term follow-up with cost-benefit efficiency and strategies for additional surgery will be helpful. These guidelines will probably be widened in scope, including different management strategies according to the following factors: age of the patient; asymptomatic presentation; patients with bleeding; patients with pregnancy and hyperthyroidism; and patients with postoperative headache, progressive ischemia, and different followup protocols. Continuous refinement of the contents of these guidelines will be necessary in the future. The work presented here represents an excellent jumping-off point for future efforts. (http://thejns.org/doi/abs/10.3171/2011.10.PEDS11467) 351 352