Notes on Hemorrhagic Stroke

Types of Stroke

  • Two Main Types:
    • Ischemic Stroke
    • Hemorrhagic Stroke (accounts for ~25% of all strokes)

Hemorrhagic Stroke Overview

  • Definition: A hemorrhagic stroke occurs when a blood vessel in the brain leaks or ruptures, leading to bleeding into the skull cavity.
  • Consequences:
    • Loss of blood from cerebral circulation.
    • Increased intracranial pressure due to the confined space of the cranium.
    • Compression of brain tissue, leading to potential brain damage.
    • Reduced blood flow downstream, resulting in tissue death.
    • Blood leaking out irritates surrounding vessels, causing vasospasm (narrowing of blood vessels), which further limits blood flow.

Effects of Vasospasm

  • Initial hemorrhage increases pressure in cranium and compresses brain.
  • Vasospasm can lead to secondary strokes due to insufficient blood delivery to affected brain tissue.

Causes of Hemorrhagic Stroke

  • Common Causes:
    1. Aneurysm:
    • Weakening and ballooning of blood vessel walls, often found at the Circle of Willis (common sites include posterior communicating artery, middle cerebral artery, anterior communicating artery).
    • Can be caused by:
      • Long-standing high blood pressure.
      • Genetic factors affecting artery walls.
    • Can rupture spontaneously or due to trauma (e.g., head injury).
    • Commonly referred to as berry aneurysms.
    1. Arteriovenous Malformation (AVM):
    • Congenital defect where arteries bypass capillary networks and connect directly to veins, maintaining high pressure.
    • Higher risk of rupture in the brain due to high pressure from the arterial side.
    • AVMs can occur anywhere but are often found in the brain.

Summary

  • Hemorrhagic strokes are serious medical emergencies characterized by the rupture or leakage of blood vessels in the brain, leading to various complications such as increased intracranial pressure, potential brain damage, and the risk of secondary strokes. The two main causes are aneurysms and arteriovenous malformations, each presenting unique risks and mechanisms of injury. Understanding these factors is crucial in emergency response and treatment options.