CADASIL (OMIM 125310) is an increasingly recognised adult-onset autosomal-dominant vascular disease that is characterised by recurrent transient ischaemic attacks and strokes (43% of patients), vascular dementia (6%), migraine with aura (40% of patients) and psychiatric disturbances (9% of patients); epilepsy has been reported in 2–10% of subjects.1 All patients revealed prominent signal abnormalities on brain magnetic resonance imaging (MRI)—leukoencephalopathy on T2- and small subcortical infarcts on T1-weighted images.2

The pathological hallmark of CADASIL is a non-amyloid and non-arteriosclerotic angiopathy, which predominantly affects the small penetrating brain arteries. Vascular lesions are characterised by degeneration and loss of smooth-muscle cells and by the presence of granular osmiophilic material (GOM) accumulating within the smooth-muscle-cell basement membrane and the surrounding extracellular matrix. Examination of several peripheral organs revealed vessel changes, including the presence of GOM deposits, providing evidence that CADASIL is a systemic arteriopathy.3

It has been reported that CADASIL is caused by single missense mutations, small in-frame deletions or splice-site mutations in the NOTCH3 gene encoding a transmembrane receptor (http://www.hgmd.cf.ac.uk/ac/gene.php?gene = NOTCH3). Almost all previously reported mutations resulted in an odd number of cysteine residues within one of the 34 epidermal growth factor (EGF)-like repeats in the …