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': 'Anterior spinal Aery thrombosis is characterized by all, except: \nSelect and explain. \nA. Loss of pain & touch, B. Loss of vibration sense, C. Loss of power in lower limb, D. Sphincter dysfunction', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer is B (Loss of vibration sense): Anterior spinal aery thrombosis does not involve the posterior column and hence vibration sense and joint positions sense (proprioception) are preserved.', 'role': 'assistant'}]