The first step in the compartmental approach to spinal and spinal cord tumors is to determine whether the lesion is osseous (within the bone), extradural non-osseous (outside the dura), intradural extramedullary (within the dura, outside the spinal cord), or intramedullary (within the spinal cord) (Fig. 11.1). This approach is because the possible differential diagnosis and surgical approach for the tumor are influenced by the compartment location of the tumor. In most cases, it is not difficult to determine the compartment where these tumors are located on MRI, but in some cases, the boundaries are ambiguous, making diagnosis difficult. If the judgment of the compartment changes, the differential diagnosis itself changes. The following are radiological clues that can help localize the compartment in which the tumor is located for diagnosis.