Imaging features of spinal osteoid osteoma with emphasis on MRI findings.

A retrospective evaluation of the imaging of 13 patients with a diagnosis of osteoid osteoma (OO) of the spine was undertaken. Available imaging included radiographs (n=10), computed tomography (CT) (n=13), bone scintigraphy (n=5) and magnetic resonance imaging (MRI) (n=13). MRI features evaluated were pattern of neural arch and vertebral body oedema and the presence of an identifiable nidus. MRI features were correlated with other available imaging. There were seven males and six females with an age range of 8-59 years. On radiographs, scoliosis was present in ten and a sclerotic pedicle in nine patients. Focal increased uptake on bone scintigraphy consistent with OO was seen in all five patients where scintigraphy was available. On CT, a nidus was identified in all patients and reactive sclerosis was seen in 12. MRI demonstrated the nidus in eight patients and unilateral neural arch oedema with anterior extension to involve the ipsilateral posterolateral vertebral body in 11. When MRI is performed in the evaluation of back pain, the presence of unilateral neural arch oedema extending to involve the posterolateral vertebral body raises the possibility of spinal OO and should prompt CT to confirm the presence of a nidus.