<prompt> Which is the least common site for the occurance of berry aneurysm?Anterior communicating aeryMiddle cerebral aeryVeebral aeryBasilar aery  <response>: 85 of berry aneurysms occur in the anterior circulation, mostly on the Circle of Willis. 3 most common anterior locations are over : anterior communicating aery, posterior communicating aery and middle cerebral aery. 10 of it occur over basilar aery and only 5 occur on veebral aery. Reference: Handbook of Neurosurgery By Mark Greenbergpage 1055. 