At what age does Moyamoya disease typically start?

Age of Onset in Moyamoya Disease

Moyamoya disease typically presents with a bimodal age distribution, with the first peak occurring around 10 years of age (first decade of life) and a second peak in adults between 30-40 years of age. 1, 2, 3

Epidemiological Patterns

Age Distribution

• First peak: Around 10 years of age (pediatric population)
• Second peak: 30-40 years of age (adult population)
• Half of patients present before 10 years of age 1

Demographic Factors

• Higher prevalence in East Asian populations (Japan, Korea)
  • 4.6 times higher incidence in Asian Americans compared to whites 1, 2
  • 2.2 times higher incidence in Black Americans compared to whites 1
  • 0.5 times lower incidence in Hispanic Americans compared to whites 1
• Female predominance with female-to-male ratio up to 2.6:1 2
• The peak age of onset appears to occur later in women than men 3

Clinical Presentation by Age Group

Pediatric Presentation (First Peak)

• Children predominantly present with ischemic symptoms:
  • Transient ischemic attacks (TIAs)
  • Ischemic stroke
  • Intellectual decline
  • Seizures
  • Involuntary movements 1, 3
• Symptoms often triggered by hyperventilation, crying, coughing, straining, or fever 1
• Characteristic electroencephalographic finding: slowing of background rhythm after hyperventilation cessation ("rebuild-up" phenomenon) 1

Adult Presentation (Second Peak)

• Adults more commonly present with:
  • Intracranial hemorrhage
  • Ischemic events (strokes or TIAs)
  • Headaches 1, 3
• Intracerebral hemorrhage in moyamoya is more often accompanied by intraventricular hemorrhage compared to hypertensive hemorrhage 3

Diagnostic Considerations

Imaging Findings

• Definitive diagnosis requires demonstration of:
  1. Stenosis of distal internal carotid artery bifurcation and proximal portions of ACA and MCA
  2. Appearance of dilated basal collateral arteries
  3. Bilateral abnormalities 1
• Catheter angiography remains the gold standard for diagnosis 1, 3
• MRA and CTA are acceptable non-invasive alternatives 1

Disease Progression

• Approximately 20% of both symptomatic and asymptomatic adult patients show disease progression 2
• Unilateral disease can progress to bilateral involvement 2
• Posterior circulation involvement is associated with worse clinical presentation and higher hemorrhage risk 2

Genetic Factors

• Strong genetic component with 6-12% of patients having a positive family history 1, 2
• RNF213 gene (particularly the R4810K variant) is the primary susceptibility gene in East Asian populations 2, 4
• Non-R4810K variants increase risk in non-East Asian populations 2
• Penetrance varies significantly: heterozygotes for RNF213 R4810K have approximately 0.67% penetrance, while homozygotes have >78% 2

Clinical Implications

• Early diagnosis is critical, especially in children, as diagnosis may be delayed due to communication limitations 1
• Different age groups require different management approaches due to varying clinical presentations
• Screening of first-degree relatives is generally not warranted unless multiple family members are affected 1
• Surgical revascularization procedures have shown benefit for symptomatic patients 5, 4

Understanding the typical age of onset and presentation patterns is essential for early diagnosis and appropriate management of moyamoya disease, potentially preventing the progressive neurological dysfunction seen in 50-66% of untreated patients 1.