Osteoid osteoma of the dens axis.

An osteoid osteoma of the dens axis was diagnosed by computed tomography and bone scintigraphy in a 14-year-old girl with a 1.5-year history of pain. No case of an osteoid osteoma of the dens axis has been published in the literature yet. Regarding its clinical and radiological appearance, this osteoid osteoma was essentially similar to osteoid osteomas in other locations, i.e., it had an osteolytic nidus surrounded by sclerosis, associated with nocturnal pain and a positive aspirin test.