Definition of Stroke

"A stroke, or cerebrovascular accident, is defined as an abrupt onset of a neurologic deficit that is attributable to a vascular cause."

• Harrison's Principles of Internal Medicine, 22E - Chapter 437: Introduction to Cerebrovascular Diseases (Wade S. Smith, J. Claude Hemphill III)

Key points from the same section:

• Cerebral ischemia is caused by a reduction in blood flow lasting longer than several seconds. Neurologic symptoms appear within seconds because neurons lack glycogen, making energy failure rapid.
• Infarction (death of brain tissue) results if flow cessation lasts more than a few minutes.
• Transient Ischemic Attack (TIA): When blood flow is quickly restored and symptoms are only transient. TIA requires that all neurologic signs and symptoms resolve within 24 hours with no evidence of brain infarction on imaging.
• Stroke has occurred if neurologic signs and symptoms last >24 hours OR brain infarction is demonstrated on imaging.

Types of Stroke:

1. Ischemic stroke - caused by thrombosis of cerebral vessels or emboli from a proximal arterial source or the heart.
2. Hemorrhagic stroke - caused by bleeding directly into or around the brain, producing neurologic symptoms via mass effect, toxic effects of blood, or raised intracranial pressure.

Epidemiology (from the same chapter):

• Stroke is the second leading cause of death worldwide, with 7.1 million deaths in 2020.
• Nearly 7 million Americans age 20+ report having had a stroke.