Aneurysm of the basilar tip. A type of posterior circulation cerebral aneurysm that accounts for just a small percentage of all aneurysms, with 90% occurring in the anterior circulation. Cerebral aneurysms are common around bifurcations, such as this one, which has the posterior cerebral artery running directly behind it. A basilar artery stroke is a sort of posterior stroke that affects the back of the brain's circulation. This type of stroke can manifest in a variety of ways since the basilar artery sends blood to the cerebellum, occipital lobes, and brainstem, all of which have diverse functions. Berry (saccular), fusiform, and mycotic aneurysms are the three forms of cerebral aneurysms. The most frequent type, known as a "berry aneurysm," is more common in adults. It can be a few millimetres long or more than two centimetres long. If you have a family history of aneurysms, you're at a higher risk.