The most common sites of intracranial aneurysms include: 1. intracranial aneurysms of the internal carotid artery: posterior communicating aneurysms are the most common, and aneurysms of the ophthalmic artery, anterior choroidal artery, and the end of the internal carotid artery are also more likely to occur; 2. aneurysms of the anterior cerebral artery: anterior communicating aneurysms are the most likely to occur, and aneurysms can also occur in the distal branches of the anterior cerebral artery, with pseudoaneurysms or traumatic aneurysms common; 3. Others: such as the bifurcation of the middle cerebral artery, the tip of the vertebrobasilar artery, the P1 and P2 segments of the posterior cerebral artery, and the posterior inferior cerebellar artery. Once the posterior inferior cerebellar aneurysm ruptures and bleeds, the condition is often severe, with sudden coma and even respiratory and circulatory instability.