Fig

Circle of Willis with anterior, middle and posterior cerebral arteries linked by communicating vessels. Berry aneurysms are seen arising where the internal carotid bifurcates into middle and anterior cerebral arteries (arrow).
Berry aneurysms


Blood is present in the sub-arachnoid space over the cerebellum. in this case the aneurysm was arising at the tip of the basilar artery.
Ruptured Berry aneurysm with subarachnoid Hge