Arterial blood supply of the brain

1. Big picture

The brain receives arterial blood from two paired systems:

1. Internal carotid artery system = anterior circulation

   • Supplies most of the cerebral hemispheres.

   • Clinically responsible for most ischemic strokes, about 80%.

2. Vertebrobasilar system = posterior circulation

   • Supplies the brainstem, cerebellum, occipital lobes, inferior temporal lobes, thalamus, and parts of the spinal cord.

   • Responsible for about 20% of ischemic strokes.

For the exam, the key is not only to name arteries, but to connect each artery to its clinical syndrome. When a patient has sudden focal neurological deficit, ask:

**Which vascular territo