What are the primary causes of hemorrhagic stroke?

Causes of Hemorrhagic Stroke

Hemorrhagic stroke results primarily from two distinct small-vessel pathologies—arteriolosclerosis (lipohyalinosis) causing deep hemorrhages and cerebral amyloid angiopathy causing lobar hemorrhages—with hypertension being the single most important modifiable risk factor across all subtypes. 1

Primary Small-Vessel Pathologies

Arteriolosclerosis (Lipohyalinosis)

• Arteriolosclerosis affects penetrating arterioles of deep brain structures including the basal ganglia, thalamus, brainstem, and deep cerebellar nuclei, producing deep-territory hemorrhages. 1
• The major risk factors driving this pathology are hypertension, diabetes mellitus, and advancing age. 1
• Hypertension remains the most important modifiable risk factor for hemorrhagic stroke, particularly for deep hemorrhages resulting from deep perforator arteriopathy. 2, 3

Cerebral Amyloid Angiopathy (CAA)

• CAA involves β-amyloid deposition in the walls of arterioles and capillaries of the leptomeninges, cortex, and cerebellar hemispheres, predominantly yielding lobar hemorrhages. 1
• Risk factors include older age and APOE ε2/ε4 alleles, with these genotypes serving as primary genetic risk factors. 1, 4
• The American Heart Association recognizes CAA as the predominant cause of lobar hemorrhages, including parietal region bleeds. 5
• Amyloid-beta accumulation increases vascular fragility and permeability, making vessels prone to rupture. 4

Macrovascular and Structural Causes

Vascular Malformations

• Arteriovenous malformations and fistulas represent approximately 32.4% of intracerebral hemorrhages in children and remain an important cause in adults. 5
• Aneurysms can cause intraparenchymal hemorrhages, though they are less common in certain regions like the parietal lobe. 5
• These structural lesions account for approximately 20% of intracerebral hemorrhages overall and are particularly important in patients under 50 years of age. 2

Tumors

• Brain tumors are associated with approximately 13.2% of intraparenchymal hemorrhages in children and also represent an important cause in adults. 5

Hematologic and Coagulation Disorders

Platelet and Clotting Factor Abnormalities

• Severe thrombocytopenia significantly increases the risk of spontaneous intracerebral hemorrhage. 5
• Deficiencies of coagulation factors—particularly factor VIII, factor XIII, and vitamin K deficiency—elevate hemorrhage risk. 5

Anticoagulant-Related Hemorrhage

• Vitamin K antagonists are associated with a twofold increase in intracerebral hemorrhage risk compared to direct oral anticoagulants. 4
• Patients with CAA face higher risk of hemorrhagic complications when receiving any antithrombotic therapy. 4

Modifiable Lifestyle Risk Factors

Beyond hypertension, several lifestyle factors independently increase hemorrhagic stroke risk in younger patients (18-49 years):

• Current cigarette smoking (adjusted OR 1.58) 6
• Alcohol consumption ≥2 drinks/day (adjusted OR 2.23) 6
• Caffeinated beverages ≥5/day (adjusted OR 1.73) 6
• Caffeine in medications (adjusted OR 3.55) 6
• Diabetes mellitus (adjusted OR 2.40), which also serves as an additional risk factor for ischemic versus hemorrhagic stroke in women 6
• Menopause (adjusted OR 2.50) 6

Prevalence and Clinical Context

• Both arteriolosclerosis and CAA are present at moderate-to-severe extents in 30-35% of individuals in longitudinal aging cohorts, yet only a minority progress to clinical hemorrhage. 1
• Approximately 85% of all strokes are ischemic, with hemorrhagic strokes accounting for the remaining 15% worldwide. 2
• Deep hemorrhages (basal ganglia, brainstem) typically result from hypertensive arteriopathy, while lobar hemorrhages are mainly caused by cerebral amyloid angiopathy or arteriolosclerosis. 2

Common Pitfalls

• Do not assume all lobar hemorrhages in elderly patients are due to CAA alone—arteriolosclerosis can also cause lobar bleeds, and hypertension remains a risk factor across all territories. 2
• Recognize that the absence of hypertension does not exclude hemorrhagic stroke—particularly in younger patients where vascular malformations, coagulopathies, and lifestyle factors play larger roles. 6
• MRI gradient-echo sequences detecting microhemorrhages indicate significantly elevated risk of recurrent intracerebral hemorrhage and should guide anticoagulation decisions. 5