Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most prevalent monogenic cerebral small vessel diseases caused by a mutation in the NOTCH3 gene. The clinical manifestations of CADASIL range from single or multiple lacunar infarcts, transient ischemic attacks, dementia, migraine with aura to psychiatric disorders. The features of brain MRI of CADASIL include multiple lacunar infarcts and diffuse leukoencephalopathy, which frequently involves external capsules and anterior temporal regions. Almost all patients with CADASIL harbor cysteine-involving mutations in NOTCH3. In Taiwan, two thirds of CADASIL patients carry NOTCH3 p.R544C mutations, and only approximately 56% of patients with CADASIL have leukoencephalopathy with anterior temporal regions involvement.