Types and Mechanisms of Stroke

Main Types of Strokes

• Hemorrhagic Stroke: occurs when an artery ruptures and bleeds within the brain.
• Ischemic Stroke: occurs when an artery gets blocked.

Types of Hemorrhagic Strokes

• Intracerebral Hemorrhage: bleeding occurs within the cerebrum.
  • Intraperichymal Hemorrhage: blood involves just the brain tissue.
  • Intraventricular Hemorrhage: blood extends into the brain's ventricles.
• Subarachnoid Hemorrhage: bleeding occurs between the pia mater and arachnoid mater of the meninges (inner layers wrapping around the brain).

Brain Anatomy Overview

• Cerebrum: divided into cerebral hemispheres, each with cortex (outer region) divided into four lobes:
  • Frontal Lobe: controls movement and executive functions.
  • Parietal Lobe: processes sensory information.
  • Temporal Lobe: handles hearing, smell, memory, visual recognition, and language.
  • Occipital Lobe: primarily responsible for vision.
• Cerebellum: aids muscle coordination and balance.
• Brainstem: controls vital functions (heart rate, blood pressure, breathing, etc.).

Blood Supply to the Brain

• Arteries:
  • Internal Carotid Arteries: turn into middle cerebral arteries (frontal, parietal, temporal lobes).
  • Anterior Cerebral Arteries: serve the medial frontal and parietal lobes, connected by the anterior communicating artery.
  • Vertebral and Basilar Arteries: supply cerebellum and brainstem.
  • Posterior Cerebral Arteries: serve occipital lobe, some temporal lobe, and thalamus.
  • Circle of Willis: a ring of blood flow compensation in case of blockages.

Causes of Intracerebral Hemorrhage

• Hypertension (high blood pressure):
  • Hyaline arteriolosclerosis: vessel wall stiffening leading to vulnerability.
  • Charcot-Bouchard Aneurysms: microaneurysms in small arteries.
• Arteriovenous Malformations: abnormal connections between arteries and veins.
• Other Conditions:
  • Vasculitis: inflammation of blood vessel walls.
  • Hemangiomas: benign vascular tumors.
  • Cerebral Amyloid Angiopathy: protein deposits in arteriolar walls.
• Secondary to Ischemic Stroke: reperfusion injury leading to hemorrhagic conversion.

Effects and Symptoms of Stroke

• Increased intracranial pressure from pooling blood.
• Downstream tissue deprived of oxygen, leading to cell death.
• Brain Herniation: brain shifts across structures like falx cerebri, tentorium cerebelli, and foramen magnum.
• Symptoms by Affected Area:
  • Anterior/Middle Cerebral Artery: numbness and muscle weakness.
  • Broca's Area (Left Frontal Lobe): slurred speech.
  • Wernicke's Area (Left Temporal Lobe): difficulties understanding speech.
  • Posterior Cerebral Artery: vision problems.
• FAST Acronym: Facial drooping, Arm weakness, Speech difficulties, Time to seek help.

Diagnosis and Treatment

• Medical Imaging: CT, MRI, and angiography to locate and size hemorrhage.
• Medication: control hypertension and relieve intracranial pressure.
• Surgical Options:
  • Craniotomy: remove part of skull to drain blood and relieve pressure.
  • Stereotactic Aspiration: needle-guided aspiration of blood under CT guidance.

Recap

• Intracerebral Hemorrhage: arterial rupture within cerebrum leading to increased pressure and downstream oxygen deprivation.
• Treatment: medication and surgery to manage pressure and remove pooled blood.
• FAST Acronym: remember to react quickly to symptoms.