F5 and Arterial thrombosis: Likewise, MTHFR gene polymorphism also increases the risk of ICH by affecting the blood clotting function via hyperhomocysteinemia which accelerates the activation of coagulation factors V,X, and XII and rises the risk of arterial thrombosis and atherosclerotic cerebrovascular diseases of large and small arteries (Diaz-Arrastia, 2000; Kelly et al., 2002; Dikmen et al., 2006).