Original: Aneurysms can commonly occur in arteries at the base of the brain ( the circle of Willis ) and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart .
Simplified: Aneurysms usually happen in arteries at the base of the brain and in the aorta ( the main artery coming out of the heart ) - this is an aortic aneurysm .