Osteoid osteoma of the proximal femur simulating spinal root compression.

In a 6 1/2-year-old boy and a 9 1/2-year-old girl, spinal root compression was suspected on the basis of muscle wasting and weakness, diminished deep tendon reflexes, and severe pain, all in a radicular distribution. However, extensive and invasive neuroradiologic evaluation failed to demonstrate compression of spinal roots. Only several months later was the correct diagnosis of osteoid osteoma reached. In one patient, the tumor was removed and on histologic examination groups of unmyelinated nerve fibers were found near the center of the tumor nidus, generally surrounding small arterioles. In the other patient parental consent was not given for the operation. The symptoms gradually subsided, although the typical radiologic features of the tumor went unchanged. The presence of unmyelinated autonomic nerve fibers in the nidus of osteoid osteoma may explain the severe pain commonly experienced by the patients. The spinal origin of such fibres can account for the radicular syndrome, while the localization of pain and sensory findings remote from the tumor site might be explained by a mechanism similar to that responsible for "referred pain."