APOE and CARASIL: The genetic factors include vascular encephalopathies such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), autosomal recessive cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), and potentially ApoE4 (Ritchie and Lovestone, 2002; Gorelick, 2004).