CADASIL is a rare mid-adult onset monogenic form of hereditary cerebral microangiopathy, caused by mutations in the NOTCH3 gene which lead to abnormal extracellular matrix accumulation of granular osmiophilic material (GOM) in the vicinity of vascular smooth muscle cells (VSMCs) causing degeneration and loss of VSMCs in small arteries and arterioles. Clinically the syndrome is manifested as migraine with aura, recurrent subcortical ischaemic events or strokes, subcortical vascular dementia and mood disorders. Diagnosis of CADASIL is established on the basis of results of genetic testing; skin biopsy and MRI. Typical MRI findings are T2 weighted hyperintensities in white matter and the capsula externa, Subcortical lacunar lesions and cerebral microbleeds are seen. Only symptomatic treatment is obtainable for CADASIL.