<prompt> The defect in berry aneurysm isDegeneration of internal elastic laminaDegeneration of mediaDeposition of mucoid material in mediaLow grade inflammation of vessel wall  <response>: Multiple aneurysms are observed in about 20-30 of cases of berry aneurysm. Such aneurysms are congenital in that defect in aerial wall may be present from bih, but actual aneurysm develops over years; thus, rupture is most likely to occur in middle-aged adults. Refer Robbins page no 1270 