Where is the bleed typically located in the brain in moyamoya disease?

Locations of Cerebral Hemorrhage in Moyamoya Disease

In moyamoya disease, hemorrhages typically occur in the basal ganglia, periventricular white matter, thalamus, and intraventricular regions, with basal ganglia hemorrhage being the most common location. 1, 2, 3

Specific Hemorrhage Locations and Distribution

Moyamoya disease can present with both ischemic and hemorrhagic manifestations, with hemorrhagic presentations being more common in adults, particularly in Asian populations. The distribution of hemorrhage locations has been well-documented:

• Basal ganglia hemorrhage: 40-44% of cases 2, 3
• Primary intraventricular hemorrhage: 30-38% of cases 2, 3
• Thalamic hemorrhage with ventricular rupture: 12-15% of cases 2, 3
• Subcortical hemorrhage: 5-6% of cases 2, 3

Pathophysiology of Hemorrhage in Moyamoya

The hemorrhages in moyamoya disease occur due to:

1. Fragile collateral vessels: The characteristic "moyamoya vessels" (abnormal vascular networks) that develop at the base of the brain are prone to rupture due to hemodynamic stress 1

2. Location of collaterals: These collateral vessels are predominantly located in the basal ganglia and periventricular white matter regions 1

3. Vascular wall abnormalities: The moyamoya vessels have thin walls and microaneurysms that increase bleeding risk 4

Imaging Characteristics

MRI can detect the site of old bleeding points and their chronological changes when studies are repeated. In patients with prior intraventricular hemorrhage, MRI performed one year or more after the event can demonstrate the primary bleeding site at the lateral wall of the lateral ventricle on proton-weighted and T2-weighted images 2, 3.

The diagnostic imaging findings in moyamoya disease include:

• Small areas of hypodensity suggestive of stroke commonly observed in cortical watershed zones, basal ganglia, deep white matter, or periventricular regions 1
• Abnormal vascular networks in the basal ganglia or periventricular white matter visible on MRA 1
• Absence of flow voids in the ICA, MCA, and ACA coupled with abnormally prominent flow voids from basal ganglia and thalamic collateral vessels 1

Clinical Significance and Prognosis

The location of hemorrhage has important prognostic implications:

• Patients with posterior circulation involvement and posterior hemorrhages have been associated with worse clinical presentation and higher rates of recurrent hemorrhage 1
• Rebleeding significantly worsens outcomes, with mortality increasing from 5-6% after first bleeding to 22-25% after rebleeding 2, 3
• Factors related to rebleeding include female sex, massive intracerebral hemorrhage, and early recurrence 3

Management Considerations

For patients with hemorrhagic moyamoya disease:

• Blood pressure control is critical in both acute and chronic stages to prevent rebleeding 2, 3
• Surgical revascularization may be considered, particularly for patients with posterior hemorrhages, as they are at higher risk of rebleeding 1
• The Japan Adult Moyamoya trial demonstrated a reduction in rebleeding with bilateral direct bypass surgery compared to medical therapy (2.7%/year versus 7.6%/year) 1

Caveat

It's important to note that while basal ganglia hemorrhage is most common, the hemorrhage pattern can vary between patients. Regular imaging follow-up is recommended as disease progression can occur in approximately 20% of both symptomatic and asymptomatic adult patients 1.