Spinal osteoid osteomas usually affect the posterior elements. In the spine, the lumbar spine followed by the cervical and then the thoracic spine are most commonly affected. The patients are usually young and present with back pain. A high index of suspicion is needed for this entity especially with MRI as the nidus and surrounding reactive sclerosis may not be diagnosed unless the lesion is suspected and then a CT is done.

On MRI, an area of edema in the posterior and lateral aspect of a vertebral body with pedicle involvement is classically seen. This region of signal abnormality shows T1 and T2 prolongation with no fatty elements within and shows homogeneous contrast enhancement. The degree of surrounding edema and enhancement is of varying grades and involvement of the paraspinal soft tissues with enhancement is classified as grade IV.

A CT is also needed after the MRI to clearly identify the nidus and the surrounding lucency. The sclerotic reaction can also be well assessed.