berry aneurysm [ME, berye + Gk, aneurysma, widening] , a small, saccular dilation of the wall of a cerebral artery. It occurs most frequently at the junctures of vessels in the circle of Willis. A berry aneurysm may be the result of a congenital developmental defect and may rupture without warning, causing intracranial hemorrhage. Smoking and hypertension increase the likelihood of rupture.
