Causes of Intracerebral Hemorrhage
The primary causes of intracerebral hemorrhage (ICH) are hypertensive arteriopathy (affecting deep brain structures) and cerebral amyloid angiopathy (affecting lobar regions), with additional causes including vascular malformations, coagulopathies, tumors, and drug use. 1, 2
Primary Causes of ICH
Small Vessel Disease
Arteriolosclerosis (Hypertensive Arteriopathy)
- Characterized by concentric hyalinized vascular wall thickening
- Primarily affects penetrating arterioles in:
- Basal ganglia
- Thalamus
- Brainstem
- Deep cerebellar nuclei
- Major risk factors: hypertension, diabetes, and advanced age 1
Cerebral Amyloid Angiopathy (CAA)
- Defined by β-amyloid peptide deposition in walls of arterioles and capillaries
- Affects:
- Leptomeninges
- Cerebral cortex
- Cerebellar hemispheres (lobar territories)
- Primary risk factors: advanced age and apolipoprotein E genotypes (ε2 or ε4 alleles) 1
Secondary Causes of ICH
Vascular Abnormalities
- Arteriovenous malformations
- Aneurysms (including mycotic aneurysms)
- Cavernous malformations
- Venous sinus thrombosis 1
Infectious Causes
- Infectious intracranial mycotic aneurysms (ICMAs)
- Associated with infective endocarditis (IE) in 2-10% of cases
- Commonly located at branching points of middle cerebral artery (55-77%)
- Caused by septic microemboli to vasa vasorum or distal branching points
- Common pathogens: S. aureus, viridans group streptococci 1
Medication and Substance-Related
- Anticoagulant use (warfarin, NOACs)
- Antiplatelet agents
- Thrombolytic therapy
- Sympathomimetic drugs (cocaine, amphetamines) 3, 4
Tumors
- Primary or metastatic brain tumors 3
Coagulopathies
- Inherited or acquired bleeding disorders 3
Risk Factors for ICH
Non-Modifiable Risk Factors
- Advanced age
- Male sex
- Asian ethnicity
- Cerebral microbleeds on imaging 4
Modifiable Risk Factors
- Hypertension (strongest risk factor)
- Current smoking
- Excessive alcohol consumption
- Hypocholesterolemia
- Chronic kidney disease 4
Pathophysiological Mechanisms of ICH
Vascular Rupture Mechanisms
- In hypertensive ICH:
- Insufficient sympathetic innervation in posterior brain circulation
- Abrupt rises in blood pressure causing higher static pressure
- According to Laplace's law, higher pressure and larger radius leads to higher wall tension
- Rupture of arterial walls previously weakened by prolonged hypertension 5
Mechanisms of Brain Injury
Direct pressure effects:
- Local compression of surrounding brain tissue
- Increased intracranial pressure
- Hydrocephalus
- Herniation
Secondary injury mechanisms:
- Cerebral edema
- Inflammation
- Biochemical toxicity from blood products (hemoglobin, iron, thrombin)
- Early hematoma expansion (common predictor of worse outcomes) 1
Anatomical Distribution of ICH
Deep ICH (Hypertensive Arteriopathy)
- Basal ganglia
- Thalamus
- Brainstem (especially pons)
- Deep cerebellar nuclei 1
Lobar ICH (Often CAA-Related)
- Cerebral cortex
- Subcortical white matter
- Cerebellar hemispheres 1
Clinical Presentation Based on Cause
Hypertensive ICH
- Often presents with sudden onset of focal neurological deficits
- Headache, vomiting, decreased consciousness
- Symptoms vary based on location of hemorrhage 1
CAA-Related ICH
- More common in elderly
- Often presents with concomitant cognitive impairment
- Predominantly lobar hemorrhages 4
Mycotic Aneurysm-Related ICH
- Fever, headache, seizures, altered sensorium
- Hemiparesis
- Sudden onset of intracranial hemorrhage in patients with IE
- Severe, localized, unremitting headache with homonymous hemianopsia 1
Understanding the causes of ICH is crucial for proper diagnosis, management, and prevention strategies. Prompt neuroimaging with CT or MRI is essential to distinguish ICH from ischemic stroke and identify potential underlying causes 1.