**1. Introduction**

Moyamoya disease is a unique cerebrovascular condition that is characterized by slowly progressive narrowing of the terminal portion of the internal carotid artery and its proximal branches. The name of this disease is derived from the dilated and fragile distal collateral vessels, which develop over time and demonstrate a characteristic "puff of smoke" appearance (see **Figure 1**) on cerebral angiography [1, 2]. On the other hand, moyamoya syndrome is traditionally considered in patients who have the characteristics vasculopathy and associated conditions, such as sickle cell disease or neurofibromatosis [3]. The incidence of moyamoya disease (MMD) is

### **Figure 1.**

*Bilateral internal carotid artery narrowing at the bifurcation with characteristic "puff of smoke" collateral circulation on cerebral angiography. Picture courtesy of Dr. Jafar (Hamad Medical Corporation).*

high in East Asia, and familial links account for 15% of the patients. It has a bimodal distribution which includes two peaks of age distribution at 5 years and 40 years [4, 5]. The pathophysiology of MMD is not a well-studied entity. However, genetic acquired, and environmental factors have been ascribed. Mutation analysis of the RNF213 gene showed a strong correlation with MMD [6]. Histologically, MMD results from fibro-cellular thickening of the intimal layer of the cerebral arteries that progress to vessel narrowing and secondary vascular proliferation. Traditionally, moyamoya disease manifests itself bilaterally; these stenotic lesions are progressive; and thus, the patients present for bilateral procedures. Classically, MMD can present as transient ischemic attacks (TIA), ischemic or hemorrhagic stroke, headache, epilepsy, and cognitive dysfunction with the occurrence of each symptoms varying depending on the age of the patient. Diagnostic criteria for MMD have been established by the Research Committee on Spontaneous Occlusions of the Circle of Willis (Moyamoya Disease) of the Ministry of Health and Welfare of Japan [7] and are presented in **Table 1**. In 1969, Takaku and Suzuki developed angiographic staging to document the progression of MMD [8] as demonstrated in **Table 2**. Medical management is aimed at reducing the risk of stroke or controlling seizures [4, 9]. Aspirin or other antiplatelet drugs are recommended to prevent strokes whereas, anti-seizure drugs should be prescribed if the patient has a seizure disorder. The definitive treatment is surgical, which involves direct or indirect revascularization techniques, or a combination of both may be used. Indirect procedures include encephaloduroarteriosynangiosis (EDAS) or encephalomyossynangiosis. In a direct revascularization procedure, the superficial temporal artery of the scalp is anastomosed directly to a cerebral artery (middle cerebral artery) to increase blood flow to the brain [10, 11]. The perioperative management of MMD presents unique challenges and mandates individualized perioperative strategy [12]. In this chapter, we review the perioperative anesthetic considerations for revascularization and nonrevascularization surgery in MMD patients with relevance to the current evidence

base and clinical guidelines. It is aimed to be a comprehensive review for residents and fellows training in the field of neuroanaesthesia.


## **Table 1.**

*Diagnostic criteria for Moyamoya disease [7].*


### **Table 2.**

*Angiographic staging for progression of MMD [8].*
