Definition of stroke
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Here is a clear, textbook-based definition of stroke:
Definition of Stroke
Stroke is a clinical syndrome characterized by the sudden onset of focal (or global) neurological deficits caused by disruption of blood supply to the brain, resulting in brain cell death.
Ischemic Stroke
The formal definition of ischemic stroke is:
Brain, spinal cord, or retinal cell death attributable to ischemia, with neuropathologic, neuroimaging, or clinical evidence of permanent injury.
Ischemic cerebrovascular disease is caused by a reduction of blood supply to the brain. The injury may be:
- Focal - occlusion of a single artery
- Multifocal - occlusion of several arteries
- Global - widespread reduction in perfusion
Approximately 85% of all strokes are ischemic, with causes distributed roughly as:
- 44% atherosclerosis
- 21% cardiogenic embolism
- 20% small-vessel (lacunar) disease
Hemorrhagic Stroke
The remaining ~15% of strokes are hemorrhagic - caused by rupture of a blood vessel leading to intracerebral or subarachnoid hemorrhage. Clinical features such as severe headache, hypertension, or impaired consciousness may raise suspicion, but brain imaging is required to differentiate ischemic from hemorrhagic stroke.
Transient Ischemic Attack (TIA)
TIA is a related but distinct entity, defined as:
A brief episode of neurologic dysfunction from focal cerebral ischemia with NO evidence of corresponding tissue injury.
Previously defined by a time limit of <24 hours, the modern definition is tissue-based - up to 30-40% of patients who clinically appear to have had a TIA will show evidence of infarction on MRI. TIA symptoms are similar to those of ischemic stroke but resolve completely without permanent injury.
Key distinction:
| Feature | Stroke | TIA |
|---|---|---|
| Neurological deficit | Focal/global | Focal |
| Tissue injury | Present (permanent) | Absent |
| Duration (old definition) | >24 hours | <24 hours |
| Modern definition basis | Tissue death on imaging/pathology | No tissue death on imaging |
- Goldman-Cecil Medicine, Chapter 376 (Ischemic Cerebrovascular Disease)
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