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': 'Fluid-filled cavity at the center of the spinal cord is seen in: \nSelect and explain. \nA. Syringomyelia, B. Brown Sequard syndrome, C. Tabes dorsalis, D. Subacute combined degeneration (SACD) of cord', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In syringomyelia, a cystic cavity forms within the spinal cord.\nThis cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord.\nTypically seen in cervical areas, there is dissociative anaesthesia (pain and\xa0 temperature ie spinothalamic sensations are lost, while posterior coloumn sensation ie proprioception and vibration are preserved) in a cape shaped distribution.\nBrown sequard syndrome is seen in hemisection of the cord .\nTabes dorsalis is syphilitic damage to cord.\nSACD occurs due to Vitamin B12 deficiency.', 'role': 'assistant'}]