A clear definition
CADASIL is an acronym for Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy. Each piece of the name describes the disease:
- Cerebral — affects the brain.
- Autosomal Dominant — inherited from one affected parent; each child has a 50% risk.
- Arteriopathy — a disease of the arteries, specifically the small ones.
- Subcortical Infarcts — small strokes deep beneath the cortex.
- Leukoencephalopathy — damage to the white matter visible on MRI.
Clinically, CADASIL is the most common monogenic (single-gene) cause of stroke and vascular dementia. It is classified as a hereditary cerebral small vessel disease (CSVD), with the small arteries supplying the deep brain tissue progressively failing over decades.
Plain-language summary
CADASIL is a genetic disease that damages the smallest blood vessels in the brain. Over time it causes migraines, strokes, mood changes, and memory problems. It runs in families. There is no cure yet, but recognition, vascular risk control, and supportive care change outcomes — and research is moving forward.
The genetics: NOTCH3 and chromosome 19
CADASIL is caused by pathogenic variants in the NOTCH3 gene, located on the short arm of chromosome 19 (19p13.12). NOTCH3 encodes a transmembrane receptor protein expressed primarily by vascular smooth muscle cells (VSMCs) and pericytes — the cells that wrap and support arteries throughout the body, including the small arteries deep in the brain.
Cysteine-altering variants in EGFr domains
The vast majority of CADASIL-causing variants are missense changes that add or remove a cysteine residue in one of the 34 epidermal growth factor-like repeat (EGFr) domains in the extracellular portion of NOTCH3. The number of cysteine residues in these domains is normally even (six per EGFr domain), and pairing forms disulfide bonds critical for folding. A pathogenic CADASIL variant leaves an unpaired cysteine, leading to misfolding, abnormal aggregation, and toxicity to vascular smooth muscle cells.
Variants in EGFr domains 1–6 are typically associated with classical, severe CADASIL, while variants in domains 7–34 tend to associate with later-onset, milder phenotypes — a major reason that CADASIL severity varies so dramatically across families.
Variant location matters
The classical/severe versus mild distinction (EGFr 1–6 vs 7–34) is one of the most important clinical correlations in CADASIL genetics — but it is not absolute. Genetic counselling should always frame predictions probabilistically, not deterministically.
How many variants exist?
More than 270 distinct pathogenic NOTCH3 variants have been reported worldwide. Some variants — for example R169C and R544C — recur in specific populations and have been studied in detail for their genotype–phenotype correlations.
How CADASIL is inherited
CADASIL is autosomal dominant, meaning a single copy of a pathogenic NOTCH3 variant is sufficient to cause disease. Practically, this means:
- Each child of a parent with CADASIL has a 50% chance of inheriting the variant.
- Both males and females are affected equally.
- The disease is typically traceable across multiple generations, although milder variants can appear "skip" generations because of variable expressivity, late onset, or earlier deaths from unrelated causes.
- De novo (new) NOTCH3 variants are rare but documented, so absence of a clear family history does not rule out CADASIL.
The biology: what's happening in the vessels
The cellular and molecular consequence of NOTCH3 misfolding is the accumulation of granular osmiophilic material (GOM) — pathognomonic deposits in the basement membrane around vascular smooth muscle cells. GOM, together with extracellular accumulation of the NOTCH3 ectodomain (NOTCH3ECD), drives:
- Loss of vascular smooth muscle cells
- Thickening and fibrosis of the small artery walls
- Impaired vasoreactivity and cerebral autoregulation
- Chronic hypoperfusion of deep white matter
- Recurrent lacunar (small, deep) infarcts
- Microbleeds and progressive white-matter injury
CADASIL is a systemic small-vessel disease — GOM has been demonstrated in skin, muscle, and other tissues. The brain dominates the clinical picture because of its extreme dependence on the perfusion supplied by these small, end-arterial vessels.
How common is CADASIL?
The clinical prevalence of CADASIL has been estimated at roughly 2–5 per 100,000 adults, but this almost certainly underestimates true frequency. Population genomic data — for example from the UK Biobank — suggest that pathogenic NOTCH3 variants may be present in approximately 1 in 300 to 1 in 400 individuals, with a substantial proportion harboring milder, late-onset variants that may not have come to clinical attention.
The take-home: many people with CADASIL are walking through the healthcare system undiagnosed. Some will never develop severe disease; many would benefit from earlier identification and aggressive vascular risk management.
Course and progression: a typical timeline
CADASIL follows a recognizable, if individually variable, life-course:
Migraine with aura
Often the first symptom — frequently more prolonged or atypical than common migraine. About 30–40% of patients experience migraine with aura.
Mood and cognitive changes begin
Apathy, depression, and subtle executive-function difficulties may emerge — often without obvious explanation, and frequently misattributed to life stress.
Stroke and TIA become prominent
Recurrent lacunar strokes and transient ischemic attacks dominate the picture. These typically occur in patients without classical vascular risk factors, which often delays the diagnosis.
Vascular cognitive impairment progresses
Stepwise decline in attention, processing speed, and executive function. Some patients develop frank dementia, gait disturbance, and pseudobulbar features.
Wide variability between individuals
Within the same family, one relative may be severely affected at 45 while another remains nearly asymptomatic at 70. Modifiers — vascular risk factors, lifestyle, possibly other genetic variants — matter.
CADASIL versus other diseases
CADASIL is regularly mistaken for other neurological conditions. Knowing the differences is essential.
| Condition | Key contrast with CADASIL |
|---|---|
| Multiple sclerosis (MS) | MS lesions are typically periventricular, juxtacortical, or in the corpus callosum, with active enhancement and CSF oligoclonal bands. CADASIL spares the corpus callosum and U-fibers, characteristically involves anterior temporal poles and external capsules, and is genetically defined. |
| Sporadic small vessel disease | Sporadic CSVD shares MRI features but typically presents later, with strong hypertensive/diabetic risk-factor profiles, no autosomal-dominant family history, and no NOTCH3 variant. |
| CARASIL | Cerebral Autosomal Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy. Caused by HTRA1 mutations. Recessive; often associated with alopecia and spondylosis. Typically more severe and earlier-onset than CADASIL. |
| HTRA1-related dominant CSVD | Heterozygous HTRA1 variants cause a dominantly inherited small-vessel disease that overlaps with CADASIL clinically and on MRI but is genetically distinct. |
| Fabry disease | X-linked lysosomal storage disease — strokes plus systemic features (renal, cardiac, dermatological). Diagnosed by enzyme assay and GLA gene testing. |
| MELAS | Mitochondrial encephalomyopathy with stroke-like episodes. Maternal inheritance, lactic acidosis, characteristic occipital lesions. |
| Migraine with prolonged aura | Without other features, isolated migraine is far more common than CADASIL — but a strong family history of stroke or atypical aura should prompt deeper evaluation. |
Prognosis and lifespan
Long-term outcome in CADASIL is highly variable. Median age at first stroke is in the 40s–50s; median age at need for assistance with daily activities is the 60s. Lifespan is typically reduced, but many individuals live for decades after diagnosis with good function — particularly when vascular risk factors are aggressively managed and supportive care is in place.
Critical prognostic levers — many of them modifiable — include:
- Blood pressure control (the single most important target)
- Smoking cessation
- Diabetes and lipid management
- Avoidance of medications and procedures that may carry CADASIL-specific risks (e.g., caution with IV thrombolytics in some clinical scenarios)
- Migraine prevention and avoidance of triptans where appropriate
- Engagement with multidisciplinary care: neurology, genetics, physiatry, mental health
Myths and misconceptions
Myth: CADASIL is too rare to consider.
Genomic data suggest pathogenic NOTCH3 variants are far more common than the reported clinical prevalence. Many people with CADASIL never receive the diagnosis.
Reality: It should be on the differential for any unexplained stroke under 60.
Especially when paired with migraine with aura, mood/cognitive change, or family history.
Myth: A normal MRI rules it out.
White matter changes typically appear by the 30s, but presymptomatic gene carriers may have minimal imaging findings.
Reality: Genetics is the gold standard.
If clinical suspicion is high, NOTCH3 testing — not MRI alone — confirms or excludes the diagnosis.
Myth: There's nothing to do because there's no cure.
This is the most damaging misconception in CADASIL care.
Reality: Diagnosis changes management.
Aggressive vascular risk control, migraine strategy, mood support, family counselling, and trial enrolment all flow from a confirmed diagnosis.
Learn more
Continue exploring CADASIL with our deep-dive pages on symptoms, diagnosis, treatment, and current research.