NOTCH3 and CADASIL: In summary, in the past 30 years since the identification of classical mutations in the CADASIL-causing gene NOTCH3, we have identified an increasing number of novel NOTCH3 variant types that exhibit clinical manifestations similar t1o those of CADASIL, implying a diversification of the NOTCH3 genotypes that cause CADASIL, partly explaining why this disease is much more prevalent than initially assumed, and is even considered to be the most common type of inherited vascular dementia (Table 1).