How CADASIL is diagnosed
CADASIL is diagnosed with an MRI showing characteristic white-matter changes (especially in the anterior temporal poles) plus genetic testing for a NOTCH3 mutation, which is the definitive test. A skin biopsy is sometimes used when genetic testing is inconclusive.
Two tools do most of the work. An MRI shows a pattern of small-vessel damage that's very suggestive of CADASIL — particularly changes in the front tips of the temporal lobes. A blood test for the NOTCH3 gene confirms it; a positive result is essentially definitive. If genetic results are unclear, a small skin biopsy can look for the tell-tale deposits.
- MRI hallmarks: white-matter hyperintensities in the anterior temporal poles (highly specific) and external capsule; lacunar infarcts; cerebral microbleeds.
- Genetic testing: detection of a pathogenic NOTCH3 variant is the gold standard (~definitive).
- Skin biopsy: electron-microscopy for GOM (~100% specific but less sensitive) or NOTCH3 immunostaining; used mainly when genetics are inconclusive.
Common questions
- What does CADASIL look like on an MRI?
- Symmetric white-matter changes, classically in the anterior temporal poles, plus small deep strokes and microbleeds.
- Is there a genetic test for CADASIL?
- Yes — a NOTCH3 test is the definitive diagnosis.
- Do I need a skin biopsy?
- Usually only if genetic testing is inconclusive.
Sources: NIH GeneReviews; MedLink; Medscape workup.
Evidence: Established
Last reviewed: July 2026.