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
Which of the following is not a feature of extramedullary tumour? 
Select and explain. 
A. Early Coicospinal signs and paralysis, B. Root pain or midline Back -pain, C. Abnormal CSF, D. Sacral sparing
D: Sacral sparing
Answer: D: Sacral sparing 
Explanation: Sacral sparing is a feature of intramedullary tumors, not extra medullary tumors. So sacral sparing is the single best answer of choice. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 2440