This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
[{'content': 'Which of the following is the most common cause of late neurological detrioration in case of cerebrovascular accident? \nSelect and explain. \nA. Rebleeding, B. Vasospasm, C. Embolism, D. Hydrocephalus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Vasospasm: Narrowing of the aeries at the base of the brain following SAH occurs regularly This vasospasm causes symptomatic ischemia and infarction in approximately 30% patients and is the major cause of delayed morbidity or death Signs of ischemia appear 4-14 days after the hemorrhage, most frequently at about 7 days. Ref: Harrisons 19th edition Pgno: 1785', 'role': 'assistant'}]