What are the key differences between ischemic and hemorrhagic stroke?

Comparison of Ischemic and Hemorrhagic Stroke

Ischemic and hemorrhagic strokes differ fundamentally in their pathophysiology, therapeutic goals, and management approaches, requiring brain imaging to definitively distinguish between them as clinical features alone are insufficient for treatment decisions. 1

Pathophysiology and Mechanism

Ischemic Stroke

• Results from insufficient blood supply to the brain due to arterial occlusion or severe stenosis 1
• The primary therapeutic objective is to resuscitate penumbral tissue to minimize disability through reperfusion 1
• Causes include large-vessel atherosclerosis (20%), small vessel disease (25%), cardiogenic embolism (20%), and cryptogenic causes (30%) 2
• Brain injury occurs from lack of oxygen and glucose delivery to neural tissue 1

Hemorrhagic Stroke

• Results from bleeding into brain parenchyma (intracerebral hemorrhage) or subarachnoid space 1, 3
• The primary therapeutic objective is to prevent rapid deterioration and early death by limiting hematoma expansion 1
• Caused primarily by hypertension for deep hemorrhages, cerebral amyloid angiopathy for lobar hemorrhages, and ruptured aneurysms for subarachnoid hemorrhage 1, 3
• Brain injury involves both primary injury from physical disruption and secondary injury from blood-derived neurotoxic factors (hemoglobin, iron) and neuroinflammation 1

Clinical Presentation

Features Suggesting Hemorrhagic Stroke

• Coma on arrival, vomiting, severe headache, current warfarin therapy, systolic blood pressure >220 mm Hg, or glucose level >170 mg/dL in non-diabetic patients more than double the chance of hemorrhage 1
• However, clinical findings overlap significantly and brain imaging is mandatory to distinguish stroke types 1

Common Presentations in Both Types

• Loss of sensation and weakness of body parts are the most common presenting symptoms in both ischemic and hemorrhagic stroke 4
• Focal neurological deficits corresponding to affected vascular territory 1

Epidemiology and Outcomes

Burden and Mortality

• The global burden of hemorrhagic stroke is higher, particularly in low- and middle-income countries, with far greater loss of productive life years compared to ischemic stroke 1
• Hemorrhagic stroke has higher case fatality and morbidity 1
• In one study, ischemic stroke mortality (15.3%) was twice that of hemorrhagic stroke (6.5%), though this varies by setting 4

Prevalence

• Ischemic stroke accounts for approximately 85-90% of all strokes, while hemorrhagic stroke accounts for 10-15% 3
• In hospital settings, ischemic stroke (65.4%) is more common than hemorrhagic stroke (34.6%) 4

Risk Factors

Ischemic Stroke Specific

• Atrial fibrillation is a major risk factor for cardioembolic stroke 2
• Large-vessel atherosclerosis affecting carotid or vertebrobasilar arteries 2
• Small vessel arteriolosclerosis 2

Hemorrhagic Stroke Specific

• Hypertension is the primary modifiable risk factor, particularly for deep hemorrhages in basal ganglia and brainstem 2, 3
• Anticoagulant use significantly increases hemorrhagic risk 3
• Cerebral amyloid angiopathy for lobar hemorrhages in elderly 1
• Vascular malformations account for approximately 20% of intracerebral hemorrhage, particularly in patients under 50 years 3
• Excessive alcohol use and liver dysfunction 2, 3

Shared Risk Factors

• Hypertension is the most common risk factor for both stroke types and predictor of stroke-related deaths 4
• Advanced age increases risk for both types 2
• Race/ethnicity influences risk, with Black individuals having twice the prevalence of whites 2

Anatomical Distribution

Ischemic Stroke

• Middle cerebral artery territory is the most common site of infarction (50.7%) 4
• Deep territories (basal ganglia, thalamus, brainstem) affected by small vessel disease 1
• Lobar territories affected by large vessel occlusions 4

Hemorrhagic Stroke

• Deep hemorrhages (basal ganglia, thalamus, brainstem) are typically caused by hypertensive arteriolosclerosis 1, 3
• Lobar hemorrhages are typically caused by cerebral amyloid angiopathy 1
• Middle cerebral artery territory is also the most common site for hematoma (29.2%) 4

Time-Dependency and Therapeutic Window

Ischemic Stroke

• Time of symptom onset is critical for thrombolytic therapy eligibility 1
• Every 30-minute delay in recanalization decreases chance of good functional outcome by 8-14% 2
• Treatment includes intravenous thrombolysis and endovascular therapy for large vessel occlusions 2

Hemorrhagic Stroke

• Initial interventions targeting hematoma growth may be more steeply time-dependent than reperfusion therapy in ischemic stroke 1
• However, the pathophysiology of secondary injury provides opportunities for a wider therapeutic window 1
• Approximately one-third of patients demonstrate substantial hematoma expansion in the first few hours, which worsens outcomes 1
• Immediate management includes blood pressure control, reversal of anticoagulation, and consideration for neurosurgical intervention 2

Cognitive Outcomes

Post-Stroke Cognitive Impairment

• Risk of post-stroke cognitive impairment varies with stroke subtype, being higher in hemorrhagic and cardioembolic stroke compared with lacunar stroke 1
• In hemorrhagic stroke, lobar location carries greater cognitive risk than deep location, likely due to underlying cerebral amyloid angiopathy 1
• Both stroke types can lead to similar functional outcomes after rehabilitation, though pathophysiology differs 5

Critical Diagnostic Distinction

Brain imaging is mandatory to distinguish ischemic from hemorrhagic stroke because clinical findings overlap and the level of accuracy from clinical features alone is insufficient to guide treatment decisions 1. This distinction is especially important given the marked differences in management, particularly regarding thrombolytic therapy for ischemic stroke versus blood pressure control and anticoagulation reversal for hemorrhagic stroke 1, 2.