Management of Moyamoya Disease in Children

Initial Management at Presentation

• Special Considerations: There are special situations such as young age, pregnancy or hyperthyroidism, that require special management when present.
• Reduction of ischemia: The main goal of surgical treatment in Moyamoya Disease is reversal of the cerebral ischemia thereby protecting the brain from future infarction from disease progression.
• Reduction of hemorrhage risk: Even though the value of surgical treatment for prevention of hemorrhage has not been proven, recent studies from Japan showed a preventive effect of revascularization surgery on re-bleeding in adults with Moyamoya Disease, especially when the bleeding site is posterior and related to choroidal or posterior cerebral arteries. The preventive effects in children and for avoidance 0f an initial bleeding are unknown (12,45,55). The reduction of the hemodynamic demand on moyamoya vessels, especially those in the basal ganglia, by providing a profuse collateral circulation surgically may be helpful for the prevention of recurrent hemorrhage.
• Direct revascularization: Direct revascularization refers to the direct anastomosis of scalp arteries to cerebral arteries. STA-MCA bypass is the typical revascularization procedure. In children, direct revascularization is, in most cases, not technically feasible, while in adults direct revascularization is. In most cases direct revascularization  is not done in children under the age of 4 years (17). It is ironic children in this age group are more likely to benefit from direct revascularization because of the increased risk of postoperative infarct. It has been shown, however, that direct revascularization performed by an experienced group is as safe as indirect revascularization but it has a potential risk of the sudden increase of CBF in a chronic severely ischemic brain resulting in a hemorrhage  and/or a hyperperfusion syndrome with neurologic deterioration (63,65}. When direct revascularization is considered, a protective effect during acute postoperative recovery phase can be expected because the cerebral ischemia is reversed immediately. Unfortunately, there are no studies comparing the rate of stroke after surgery between direct revascularization and indirect revascularization in children with Moyamoya Disease. Although angiographic outcome has been reported to be superior to indirect revascularization in patients with direct revascularization, there is no difference in the clinical outcome of these patients (25). In addition, the patency is maintained in only 53% of STA-MCA bypasses in pediatric Moyamoya Disease while neovascularization occurs in more than 90% of cases after indirect revascularization (19). When combined revascularization is performed, most revascularization is established through indirect sites after long-term follow-up in children (32). Therefore, it is difficult to say the superiority of direct revascularization compared to indirect revascularization. Further studies are required in terms of as its actual clinical gains, safety or surgical indications.
• Indirect revascularization: Indirect revascularization refers to the intracranial insertion of the scalp’s galea or muscle layers to promote ingrowth of blood vessels to the ischemic brain.  In children the response to indirect revascularization is excellent even though it takes one or two weeks to get symptomatic stabilization.  In adults, the increase of CBF by indirect revascularization is often unsatisfactory.  The name of operation depends on the tissue inserted such as EDAS, encephalogaleo (periosteum) synangiosis (EGS), encephalomyosynangiosis, or EDAMS. In pediatrics, indirect revascularization is still preferable based on the favorable postoperative course, safety and long-term accumulation of data.

Adjunctive Therapies

• Medical therapy: While there is no medical therapy known to effectively treat moyamoya, some centers advocate the use of agents to improve blood flow (aspirin, Plavix, etc.) to aid in circulation.  In addition, medical therapies targeting secondary effects of moyamoya (anti-seizure or anti-headache medication) may be warranted.

Follow-up

• Ischemic symptoms: The ischemic symptoms often diminish or disappear after revascularization surgery. These improvements can be observed quickly, often by 2 weeks after surgery, even in cases of indirect revascularization surgery.
• Headache: Even patients in whom ischemic symptoms disappear may complain of headache. Postoperative continued progressive narrowing of intracranial arteries accompanies dilatation of collateral vessels. During this period, headache may persist even in the absence of other ischemic symptoms and can sometimes be treated with medical therapy, such as verapamil.
• New involvement of posterior cerebral arteries: After revascularization surgery for the cerebral hemispheres of both sides, patients older than 5 years usually show stable course. However, 15 – 20% of patients in some series may later develop involvement of posterior cerebral arteries, which ultimately could require additional surgery.
• Neuroimaging: There is no consensus on the frequency of neuroimaging follow-up. For those with stabilized symptoms, neuroimaging studies for evaluation of CBF are performed 6 months after surgery, then repeat with increasing interval until adulthood.
• Duration of follow-up: There is no consensus on the duration of follow-up. We prefer continuing follow-up into adulthood with long intervals, scanning every 5-10 years.