Mutations in Notch3 are the cause of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), an inherited small vessel disease leading to subcortical strokes and vascular dementia. The phenotypic presentation is variable but remarkable for a high frequency of migraine with aura. Magnetic resonance images show a microangiopathic pattern of lesions. Prominent involvement of the temporopolar white matter and involvement of the temporopolar arcuate fibers are conspicuous findings seen in many patients, The underlying angiopathy is characterized by a unique type of ultrastructural basal lamina deposits and by degeneration of vascular smooth muscle cells which are the major source of Notch3 expression. In line with these findings there is evidence for a functional impairment of vascular smooth muscle cells. CADASIL has opened a new perspective in studying basic mechanisms of vessel wall degeneration and ischemic tissue damage related to small vessel disease. Copyright (C) 2002 S. Karger AG, Basel.