This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Dissociated sensory loss is seen in \nSelect and explain. \nA. Syringomyelia, B. Vitamin B12 deficiency, C. Transverse myelitis, D. Pellagra', 'role': 'user'}, {'content': "Answer: A \nExplanation: Harrison's principles of internal medicine 17th edition. * The classical presentation in syringomyelia is a central cord syndrome consisting of a dissociated sensory loss and areflexic weakness in upper limbs", 'role': 'assistant'}]