This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Most Common cause of subarachnoid hemorrhage is: March 2009 \nSelect and explain. \nA. Rupture of bridging veins, B. Saccular aneurysm rupture, C. Hypeension, D. Idiopathic', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Saccular aneurysm rupture Excluding head trauma, the most common cause of subarachnoid hemorrhage (SAH) is hemorrhage from an intracranial aneurysm. Other causes include vascular malformations, tumors, and infection. The management of aneurysmal SAH has changed due to superiority of early surgery for clipping of ruptured aneurysms. This superiority derives from the relative safety of early aneurysm surgery and the major threat of early rebleeding (approximately 25% in three weeks after SAH).', 'role': 'assistant'}]