Cerebral arterial circle

Looks like

A ring of arteries under the brain (circle of Willis), linking both carotid arteries with the basilar artery around the pituitary stalk.

What it does

Lets blood cross from one supply to another, so a slowly narrowed artery can be bypassed; complete rings are present in fewer than half of people.

Keeping it well

Most brain aneurysms sit on this ring. A sudden worst-ever headache (thunderclap) may be a burst aneurysm — call an ambulance.

Its parts

• Right posterior communicating artery
• Left posterior communicating artery
• Anterior communicating artery
• Precommunicating part of right posterior cerebral artery
• Precommunicating part of left posterior cerebral artery

Related conditions

• Brain aneurysm
• Carotid artery stenosis
• High blood pressure
• High cholesterol
• Hypothermia & frostbite
• Ischaemic stroke
• Kawasaki disease
• Metabolic syndrome
• Orthostatic hypotension & POTS
• Peripheral artery disease
• Phaeochromocytoma & hyperaldosteronism
• Pre-eclampsia
• Raynaud's phenomenon
• Retinal artery occlusion (eye stroke)
• Sepsis
• Shock (circulatory failure)
• Takayasu arteritis
• Transient ischaemic attack
• Vasculitis (GCA & others)