What is a Stroke?
A stroke is an acute episode of focal or global neurological dysfunction caused by vascular injury to the brain, spinal cord, or retina resulting from either ischemia (blocked blood flow) or hemorrhage (bleeding), with symptoms persisting for at least 24 hours or until death. 1, 2
Core Definition and Classification
Stroke represents a clinically defined syndrome of sudden-onset neurological deficits attributed to vascular injury of the central nervous system 3. The condition is fundamentally divided into two major categories:
Ischemic Stroke (85% of cases)
- Definition: Acute episode of focal cerebral, spinal, or retinal dysfunction caused by infarction (tissue death) of central nervous system tissue 2
- Results from blocked blood flow to brain tissue
- Caused primarily by:
- Small vessel arteriolosclerosis (deep perforator disease)
- Cardioembolism (blood clots from the heart)
- Large artery atherothromboembolism (carotid or vertebral artery disease)
- Arterial dissection (particularly in younger patients)
- Other determined causes (hypercoagulable states, sickle cell disease) 4, 3
Hemorrhagic Stroke (15% of cases)
- Definition: Acute episode of focal or global cerebral or spinal dysfunction caused by bleeding into the brain parenchyma (intracerebral hemorrhage) or surrounding spaces (subarachnoid, subdural, epidural) 2
- Locations include:
- Deep hemorrhages (basal ganglia, brainstem) - typically from hypertensive arteriopathy
- Lobar hemorrhages - mainly from cerebral amyloid angiopathy
- Cerebellar hemorrhages
- Caused by vascular malformations, aneurysms, or venous sinus thrombosis in younger patients 3
Key Distinguishing Features
Time criterion: The traditional definition requires symptoms lasting ≥24 hours, which distinguishes stroke from transient ischemic attack (TIA) 5, 6. However, modern imaging has refined this - if brain imaging shows tissue infarction, the event is classified as stroke regardless of symptom duration 2, 7.
Vascular mechanism: The neurological deficit must be attributed to a vascular cause (not tumor, infection, or trauma) and confirmed by clinical assessment, often supplemented by brain imaging (CT or MRI) 5, 2.
Clinical Significance
Stroke is the second leading cause of death and disability worldwide 3. The acute loss of neurological function can be:
- Focal: Affecting specific brain regions (weakness on one side, speech difficulty, vision loss)
- Global: Affecting consciousness or multiple brain functions simultaneously 1, 2
Important Clinical Caveat
The term "cerebrovascular accident" (CVA) is outdated and should be avoided 8. This terminology incorrectly implies stroke is an unpredictable accident, when in fact stroke results from identifiable, modifiable risk factors - particularly hypertension, which is the single most important modifiable risk factor 4, 3. The condition should be referred to as "stroke" or "cerebrovascular disease" to emphasize its preventable nature.