Cortical Bloodflow and Vascular Anatomy

Cortical Blood Flow

  • Circle of Willis: Significant vascular structure providing collateral blood circulation to the brain.
    • Major arteries included:
    • Middle cerebral artery
    • Internal carotid artery
    • Anterior cerebral artery
    • Posterior cerebral artery
    • Anterior communicating artery
    • Posterior communicating artery
    • Anterior choroidal artery
    • Ophthalmic artery
    • Basilar artery
    • Vertebral artery
    • Superior and inferior cerebellar arteries
    • Anterior inferior cerebellar artery
    • Posterior inferior cerebellar artery
  • All arteries contribute to maintaining brain perfusion and function.

Vasculature Pathology Terms

  • Thrombus: A stationary blood clot that forms within a blood vessel.
  • Embolus: Any material (e.g. thrombus) that travels through the bloodstream and can cause blockage in vessels, leading to possible stroke.
  • Ischemia: A condition in which blood flow (and thus oxygen) is insufficient to supply the tissues, leading to tissue damage.
  • Stroke: A neurological event resulting from ischemic or embolic blockage of blood supply to brain tissues.
  • Infarct: An area of dead or necrotic tissue resulting from obstruction to the blood supply.

Blood Supply to the Thoracic Cord

  • Circulation Overview:
    • Vascular supply plays a critical role in spinal cord function and health.
    • Anterior and posterior circulation systems supply different areas.

Anterior and Posterior Circulation

  • Internal Carotid System: Supplies the anterior circulation of the brain.
  • Vertebrobasilar System: Responsible for supplying the posterior circulation.
  • Neurovasculature implications:
    • Key branches include:
    • AICA (Anterior Inferior Cerebellar Artery) branches into labyrinthine arteries supplying the cochlea and cranial nerves VII and VIII.
    • PICA (Posterior Inferior Cerebellar Artery) as the first branch of vertebral arteries, highly at risk during posterior fossa surgeries.

Cerebral Blood Supply and Metabolic Needs

  • The brain has high metabolic requirements, consuming:
    • 20% of blood pumped by the heart
    • 20% of the body's oxygen
  • Consequences of blood flow cessation:
    • 5-10 seconds: Temporary neuronal changes.
    • 5-10 minutes: Leads to permanent neuronal damage or death.

Systemic Circulation Overview

  • The circulatory system is divided into:
    • Pulmonary Circulation: Blood flow from the right side of the heart to the lungs for oxygenation and back to the left side of the heart.
    • Systemic Circulation: Distributes oxygen-rich blood from the left side of the heart to tissues and organs throughout the body.

Vascular Anatomy Overview

  • Tunica Intima:
    • Composed of endothelium and loose connective tissue including internal elastic lamina.
  • Tunica Media: Typically thicker in arteries; consists of smooth muscle and elastic fibers.
  • External Elastic Lamina and Tunica Externa: Surround the arteries, aiding structural integrity.

Aorta and Major Branches

  • Aorta: Major artery supplying blood to the body, branching off into:
    • Brachiocephalic Trunk: Supplies right arm, head, brainstem, and cerebellum.
    • Left Common Carotid: Supplies the left anterior head and face.
    • Left Subclavian: Supplies the left arm.
    • Right Common Carotid: Supplies the right anterior head and face.
    • Right Internal and External Carotid:
    • Internal Carotid: Supplies anterior head.
    • External Carotid: Supplies face.

Cerebral Artery Function

  • Middle Cerebral Arteries: Supply blood to the lateral aspects of the frontal, parietal, and superior temporal lobes.
  • Anterior Cerebral Arteries: Supply medial aspects of the frontal and parietal lobes.
  • Basilar Artery: Supplies brainstem and cerebellum.
  • Vertebral Arteries: Supply both cerebellum and brainstem areas, significant for coordination and balance.

Circle of Willis Functions

  • Collaboratively provides collateral blood flow to the brain, stabilizing perfusion, especially in cases of vascular occlusion.
    • Comprises anterior and posterior communicating arteries to link different vascular territories.

Dural Venous Sinuses

  • Important venous structures involved in draining blood from the brain, contributing to cerebral venous circulation.
    • Superior Sagittal Sinus: Drains superior region.
    • Inferior Sagittal Sinus: Drains inferior region.
    • Transverse and Sigmoid Sinuses: Major pathways draining blood toward the heart.

Spinal Cord Perfusion

  • Spinal Cord Vasculature: Includes posterior spinal artery, anterior spinal artery, and their branches, essential for nutrient delivery and waste removal.
  • Artery of Adamkiewicz: Key artery providing blood supply to the lower spinal cord; significant in surgical considerations to prevent ischemia.

Conclusion

  • Understanding the intricate details of vascular anatomy and perfusion pathways is crucial for identifying and treating cerebrovascular diseases and conditions.