CADASIL is a rare, autosomal dominant genetic disorder caused by a mutation of the NOTCH3 gene on the 19th chromosome. Hallmark symptoms of CADASIL may include: recurrent strokes, cognitive impairment, migraine with aura, and psychiatric disturbances. These symptoms are caused by damage to small blood vessels, especially those within the brain. The specific symptoms and severity of the disorder can vary greatly among affected individuals, even among members of the same family. Despite this variability, most individuals (approximately three out of four patients) experience recurrent stroke or transient ischemic attacks (TIAs), beginning at 40-50 years of age. CADASIL affects all races and both genders equally, each child of a parent with CADASIL has a 50% chance of having the disorder.

CADASIL is an acronym that stands for:
(C)erebral - relating to the brain
(A)utosomal (D)ominant - a form of inheritance in which one copy of an abnormal gene is necessary for the development of a disorder
(A)rteriopathy - disease of the arteries (blood vessels that carry blood away from the heart)
(S)ubcortical - relating to specific areas of the brain supplied by deep small blood vessels
(I)nfarcts - tissue loss in the brain caused by lack of blood flow to the brain, which occurs when circulation through the small arteries is severely reduced or interrupted
(L)eukoencephalopathy - lesions in the brain white matter caused by the disease and observed on MRI.

The diagnostic test for CADASIL was discovered in the early 2000s. Many individuals have been misdiagnosed with Multiple Sclerosis and other neurologic disorders.