What are the different kinds of strokes?

Types of Strokes

Strokes are broadly classified into two major categories: ischemic strokes (85% of all strokes) and hemorrhagic strokes (15% of all strokes), each with distinct subtypes that affect patient outcomes and treatment approaches. 1

Ischemic Strokes

Ischemic strokes occur when blood flow to the brain is blocked by a clot or narrowing of blood vessels. According to the TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification, ischemic strokes are divided into five major subtypes:

1. Large-Artery Atherosclerosis

   • Occurs when there is significant stenosis (≥50%) or occlusion of a major brain artery or branch cortical artery due to atherosclerosis 2
   • Often preceded by TIAs in the same arterial distribution 2
   • Mechanism involves either artery-to-artery embolism or hemodynamic insufficiency 2
   • Typically presents with cortical infarcts in the distribution of a large cerebral artery 2

2. Cardioembolism

   • Results from emboli originating from the heart or aorta 2
   • Presents as cortical or large subcortical infarctions with an identifiable high-risk cardiac source 2
   • Associated with the highest mortality rate (22.6% within 90 days) among ischemic stroke subtypes 2
   • Lowest survival rate (55% at 2 years) compared to other stroke subtypes 2

3. Small-Artery (Lacunar) Stroke

   • Small infarcts (<1.5 cm) in the deep brain structures or brain stem 2, 3
   • Caused by occlusive arteriopathy of small penetrating arteries 2
   • Typically associated with diabetes or hypertension rather than atherosclerosis 2
   • Presents with specific lacunar syndromes such as pure motor hemiparesis 3
   • Has the highest survival rate (85% at 2 years) among stroke subtypes 2

4. Uncommon Causes of Stroke

   • Includes nonatherosclerotic vasculopathies, hypercoagulable states, hematologic disorders 2
   • No restriction on size or location of the infarct 2
   • More common in younger patients (<50 years) 4
   • Examples include arterial dissections, arteritis, and hereditary connective tissue disorders 4

5. Undetermined Causes of Stroke

   • Comprises more than one-third of all strokes 2
   • Includes cases with two or more potential mechanisms identified 2
   • Also includes patients with incomplete or negative diagnostic evaluations 2

Hemorrhagic Strokes

Hemorrhagic strokes account for approximately 15% of all strokes worldwide and are categorized by location and cause:

1. Deep Hemorrhages

   • Occur in the basal ganglia and brainstem 1
   • Usually result from deep perforator (hypertensive) arteriopathy 1

2. Cerebellar Hemorrhages

   • Located in the cerebellum 1
   • Can cause rapid deterioration due to brainstem compression 1

3. Lobar Hemorrhages

   • Primarily caused by cerebral amyloid angiopathy or arteriolosclerosis 1
   • Located in the cerebral lobes 1

4. Hemorrhages Due to Macrovascular Lesions

   • Caused by vascular malformations, aneurysms, or cavernomas 1
   • Account for about 20% of intracerebral hemorrhages 1
   • More common in young patients (<50 years) 1

Transient Ischemic Attack (TIA)

TIA is a related condition that presents with stroke-like symptoms but traditionally resolves within 24 hours:

• Modern definition: a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without evidence of infarction 5
• High risk of subsequent stroke: 8.8% at 7 days and 11.6% at 90 days 5
• With modern imaging, up to one-third of patients with symptoms lasting <24 hours show evidence of infarction 2, 5
• Requires urgent evaluation and treatment due to high early stroke risk 5, 6

Clinical Implications

• Stroke subtype is a strong predictor of long-term survival and outcomes 2
• Cardioembolic strokes have the highest mortality, while small-vessel (lacunar) strokes have the best prognosis 2
• Treatment approaches differ based on stroke subtype 6
• Accurate classification requires comprehensive diagnostic testing including brain imaging and vascular studies 2

Diagnostic Approach

• Brain imaging (CT or MRI) is essential to distinguish between ischemic and hemorrhagic strokes 2
• Vascular imaging helps identify large artery stenosis or occlusion 5
• Cardiac evaluation is necessary to detect potential sources of cardioembolism 2
• Modern imaging techniques have improved the ability to differentiate TIA from stroke 5

Understanding stroke subtypes is crucial for determining appropriate treatment strategies and predicting outcomes, with mortality, morbidity, and quality of life varying significantly between different stroke types 2, 1.