M02.05.001 Arterial Supply

🧠 Introduction

The central nervous system (CNS) demands a continuous and rich supply of oxygen and nutrients. Despite representing only 2% of total body mass, the brain consumes nearly 20% of total oxygen at rest. Even brief interruptions in blood flow can lead to irreversible ischemic injury.

In this article, we will explore:

• The arterial supply to the brain and spinal cord
• The Circle of Willis
• Disorders related to compromised CNS perfusion

🫀 Arterial Supply to the Brain

The brain is mainly supplied by two paired arteries:

• Internal carotid arteries
• Vertebral arteries

These vessels arise from the neck and enter the cranial cavity, eventually forming the Circle of Willis, which gives rise to cerebral branches.

🔹 Internal Carotid Arteries (ICA)

• Originate at the C4 level from the common carotid artery
• Ascend through the carotid sheath
• Enter the cranium via the carotid canal (temporal bone)
• Pass through the cavernous sinus

Branches:

🔹 Vertebral Arteries

• Arise from the subclavian arteries
• Ascend via the foramen transversarium (cervical vertebrae)
• Enter cranium through the foramen magnum

Branches:

The two vertebral arteries unite to form the basilar artery, which gives rise to cerebellar and pontine branches before bifurcating into posterior cerebral arteries (PCA).

🔄 Circle of Willis

An anastomotic ring of arteries located at the base of the brain, crucial for collateral circulation.

Components:

• Anterior cerebral arteries (ACA)
• Internal carotid arteries (ICA)
• Posterior cerebral arteries (PCA)

Connecting arteries:

• Anterior communicating artery
• Posterior communicating arteries

This structure maintains perfusion even when one part of the system is compromised.

🗺️ Regional Cerebral Blood Supply

🧬 Arterial Supply to the Spinal Cord

Supplied by longitudinal arteries and segmental reinforcements:

Primary Arteries:

Supplementary Arteries:

• Segmental medullary arteries: Enter via intervertebral foramina
• Radicular arteries: Supply nerve roots
• Great anterior segmental artery (of Adamkiewicz): Major reinforcement to lower spinal cord, usually on the left side

🩺 Clinical Relevance

🧠 Stroke (Cerebrovascular Accident)

Sudden loss of neurological function due to impaired brain blood supply.

Causes:

• Thrombosis: Local clot formation
• Embolism: Clot from elsewhere (e.g. carotid)
• Hypoperfusion: Shock/low blood pressure
• Hemorrhage: Vessel rupture

⚠️ Embolism is the most common.

💥 Intracerebral Aneurysms

• Abnormal arterial dilation (≥50% diameter)
• Common in Circle of Willis
• Silent until rupture → subarachnoid hemorrhage
• High mortality without urgent surgical treatment

🧍 Spinal Cord Infarction

• Rare but devastating
• Common causes: trauma, atherosclerosis, external compression

Presentation:

• Paralysis
• Reflex loss
• Preserved posterior column function (in ~95%)

✅ Key Points to Remember

• The brain is supplied by ICA and vertebral arteries
• The Circle of Willis provides redundancy to protect against ischemia
• The anterior spinal artery and artery of Adamkiewicz are vital for spinal cord perfusion
• Strokes and aneurysms are common disorders of CNS arterial supply

📚 Bibliography

• Snell, R. S. Clinical Neuroanatomy. 8th ed.
• Standring, S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed.
• Moore, K. L. Clinically Oriented Anatomy. 8th ed.
• TeachMeAnatomy: Arterial Supply to the Brain
• Radiopaedia: Circle of Willis