Types of Strokes
Strokes are divided into two major categories: ischemic strokes (80-87% of cases) and hemorrhagic strokes (13-20% of cases), with ischemic strokes further classified into five key subtypes based on their underlying mechanism. 1, 2, 3
Major Stroke Categories
Ischemic Strokes (80-87% of all strokes)
Ischemic strokes occur when blood vessels to the brain become blocked, leading to cerebral infarction. 1, 2 These are classified into five distinct subtypes:
1. Large-Artery Atherosclerosis (20% of ischemic strokes)
- Results from significant stenosis or occlusion of major brain arteries or branch cortical arteries due to atherosclerotic plaque buildup 1, 4
- Can affect extracranial vessels (carotid, vertebral arteries) or intracranial segments 1, 4
- Typically presents with cortical infarcts in the distribution of a large cerebral artery and may be preceded by TIAs in the same arterial territory 4
2. Cardioembolic Stroke (20% of ischemic strokes)
- Caused by emboli originating from the heart or aorta, most frequently from atrial fibrillation 1, 4
- Presents as cortical or large subcortical infarctions with an identifiable high-risk cardiac source 4
- Carries the highest mortality rate among all ischemic stroke subtypes 4
3. Small-Vessel (Lacunar) Stroke (25% of ischemic strokes)
- Small infarcts (<1.5 cm diameter) in deep brain structures or brainstem caused by occlusive arteriopathy of small penetrating arteries 1, 4, 5
- Strongly associated with diabetes and hypertension rather than atherosclerosis 4
- Has the best prognosis among ischemic stroke subtypes, with 85% survival at 2 years 5
4. Stroke of Other Determined Cause
- Includes uncommon etiologies such as arterial dissection, hypercoagulable states, sickle cell disease, and other specific vascular pathologies 1, 4
- Particularly important to identify in younger patients (<50 years) where dissection is more common 3
5. Cryptogenic Stroke (30% of ischemic strokes)
- Strokes where the exact cause remains unknown despite comprehensive evaluation 1
- Reflects inadequacy or timing of diagnostic workup to visualize the occluded artery or localize the embolic source 1
Hemorrhagic Strokes (13-20% of all strokes)
Hemorrhagic strokes result from ruptured blood vessels in or around the brain. 1, 2
1. Intracerebral Hemorrhage (ICH) (10% of all strokes)
- Bleeding directly into brain parenchyma 1, 2
- Subtypes based on location:
- Primary risk factors include hypertension (the number one cause), bleeding disorders, African-American ethnicity, aging, vascular malformations, excessive alcohol use, and liver dysfunction 1
- Approximately 20% are caused by macrovascular lesions (vascular malformations, aneurysms, cavernomas) or venous sinus thrombosis, particularly in younger patients 3
2. Subarachnoid Hemorrhage (SAH) (3% of all strokes)
- Bleeding into the subarachnoid space surrounding the brain 1, 2
- Primary cause is ruptured cerebral aneurysm 1
Transient Ischemic Attack (TIA)
TIA is defined as a brief episode of neurological dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than 1 hour and without evidence of infarction on imaging. 1
- The traditional definition required symptoms lasting <24 hours, but modern imaging shows up to one-third of patients with symptoms <24 hours have evidence of infarction 4
- TIAs share the same pathogenetic mechanisms as ischemic strokes and carry significant stroke risk: up to 10.5% at 90 days, with greatest risk in the first week 1
- TIA and minor strokes combined account for 65% of all acute ischemic cerebrovascular events 6
Clinical Significance
Stroke subtype classification is critical because it strongly predicts long-term survival, guides treatment approaches, and determines secondary prevention strategies. 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