What percentage of brain blood is provided by vertebral arteries and at what rate?

• A. 25% at 120-180 ml/min
• B. 10% at 30-50 ml/min
• C. 15% at 40-60 ml/min
• D. 20% at 50-100 ml/min

Answer: (D)

Vertebral arteries feed the posterior circulation of the brain. They account for roughly one-fifth of the brain’s blood flow, with the rest coming from the internal carotid arteries for the anterior circulation. In a resting adult, total cerebral blood flow is about 750 ml per minute, so the vertebrobasilar supply is on the order of 100 ml/min (roughly 15–20% of total flow). Therefore, the figure that states about 20% of brain blood flow and a flow around 50–100 ml/min aligns with these typical values. The rate can vary with body demands and blood pressure, but this range reflects the common resting figure.