Pathology of subarachnoid haemorrhage
Berry aneurysms tend to arise at arterial junctions in the Circle of Willis
Between posterior communicating and internal carotid: posterior communicating artery aneurysm.
Between anterior communicating and anterior cerebral arteries: anterior communicating artery aneurysm
At bifurcation of middle cerebral artery: middle cerebral artery aneurysm
The aneurysm then ruptures and blood goes into the subarachnoid space, leading to the symptoms.