**2.3 The role of lipid-lowering therapy in Moyamoya disease**

The benefit of lipid-lowering treatment in Moyamoya disease is unclear. There is no direct clinical trial regarding lipid-lowering therapy in Moyamoya disease. Among those lipid-lowering drugs, statins are the only sub-group that give benefit for primary and secondary ischemic stroke prevention in patients with presumed atherosclerotic disease [26, 27]. The indirect evidence from Church et al.'s study demonstrated that statins, the essential lipid-lowering drugs for atherosclerosis treatment, may reduce unilateral Moyamoya disease progression [28]. The Japanese guidelines for Moyamoya disease management do not recommend routine prescribing lipid-lowering treatment, except for presenting concurrent dyslipidemia [22]. It is reasonable to lower the low-density lipopretien (LDL) below 100 mg/ dL as recommended in stroke patients with presumed atherosclerotic disease (**Table 3**).
