What are the main types of strokes?

Main Types of Stroke

Strokes are fundamentally divided into two major categories: ischemic strokes (accounting for approximately 85% of cases) and hemorrhagic strokes (accounting for approximately 15% of cases), with ischemic strokes further subdivided into five distinct subtypes based on etiology. 1

Ischemic Stroke (85% of all strokes)

Ischemic strokes result from complete occlusion of an artery, leading to inadequate blood flow and brain tissue infarction. 2, 1 The American Heart Association recommends classifying ischemic strokes into five specific subtypes using the TOAST classification system: 3, 4

1. Large-Artery Atherosclerosis

• Occurs when there is ≥50% stenosis or complete occlusion of a major cerebral artery due to atherosclerotic disease 3, 4
• Typically presents with cortical infarcts in the distribution of large cerebral arteries 3, 4
• Often preceded by transient ischemic attacks (TIAs) in the same arterial distribution 3, 4
• Mechanism involves either artery-to-artery embolism or hemodynamic insufficiency 3

2. Cardioembolic Stroke

• Results from emboli originating from the heart or aorta, causing arterial occlusion 3, 4
• Presents as cortical or large subcortical infarctions with an identifiable high-risk cardiac source 3, 4
• Has the highest mortality rate among all ischemic stroke subtypes 4
• Requires exclusion of atherosclerotic narrowing in the parent large artery to confirm diagnosis 3

3. Small-Artery (Lacunar) Stroke

• Diagnosed when patients present with lacunar syndromes (such as pure motor hemiparesis) and small lesions <1.5 cm on neuroimaging 3, 4
• Caused by occlusive arteriopathy of small penetrating vessels deep in the brain or brainstem 3, 4
• Strongly associated with diabetes and hypertension rather than atherosclerosis 3, 4
• Has the best prognosis among ischemic stroke subtypes, with 85% survival at 2 years 4, 5

4. Uncommon Causes

• Identified through diagnostic testing and include nonatherosclerotic vasculopathies, hypercoagulable states, or hematologic disorders 3
• No restriction on infarct size or location on brain imaging 3
• Particularly important to identify in younger patients (<50 years) where extracranial dissection and other atypical causes are more prevalent 1

5. Undetermined Causes

• Accounts for more than one-third of all ischemic strokes 3
• Includes patients with two or more potential mechanisms identified or those with incomplete/negative evaluations 3

Hemorrhagic Stroke (15% of all strokes)

Hemorrhagic strokes result from rupture of cerebral blood vessels with bleeding into surrounding tissue. 2, 1 These are subdivided into two main categories:

Intracerebral Hemorrhage (ICH)

• Accounts for 10-15% of all strokes 6
• Deep hemorrhages (basal ganglia, brainstem): Primarily caused by hypertensive arteriopathy and arteriolosclerosis 6, 1
• Lobar hemorrhages: Mainly caused by cerebral amyloid angiopathy or arteriolosclerosis 1
• Cerebellar hemorrhages: Can result from similar mechanisms 1
• Vascular malformations (arteriovenous malformations, cavernomas, aneurysms) account for approximately 20% of ICH, particularly in patients under 50 years 6, 1
• Other causes include bleeding disorders, anticoagulant use, excessive alcohol consumption, and liver dysfunction 6

Subarachnoid Hemorrhage (SAH)

• Comprises approximately 3% of all strokes 6
• Ruptured cerebral aneurysms are the leading cause 6
• Less common subtypes include intracranial dissection, perimesencephalic hemorrhage, and cortical SAH 6
• Presents most commonly with sudden onset of severe headache 7

Critical Clinical Considerations

Uncontrolled hypertension remains the most critical modifiable risk factor for hemorrhagic stroke, while also contributing significantly to ischemic stroke risk. 6, 1 Stroke subtype is a strong predictor of long-term survival and outcomes, with cardioembolic strokes having the highest mortality and lacunar strokes having the best prognosis. 4 Accurate classification requires comprehensive diagnostic testing, including brain imaging (CT or MRI) to distinguish ischemic from hemorrhagic stroke, vascular imaging to identify stenosis or occlusion, and cardiac evaluation to detect potential embolic sources. 4