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19 yo M, Back Pain


Findings, DDx at this point
Osteoid Osteoma

• Initial images showed scoliosis and a sclerotic right pedicle in the T12 vertebra, this was confirmed on the oblique.
• DDX at this point includes hyperplasia contaraleteral hypoplasia of the pedicle, metastatic disease (unlikely in a patient this young), infection sclerosing osteomyelitis, other bone tumors (e.g. osteosarcoma).
• Bone scan confirms increased uptake in this area (and also shows it to be an isolated lesion), and CT scanning demonstrates the nidus.

MRI Imaging (Different Patient)

• MRI (above, left) shows a large zone of edema surrounding a different patient who had osteoid osteoma in the left femoral neck.
• Even with MR, this still might be infection, as the nidus isn’t always demonstrated.
• The “double density” sign on bone scan (far right) is said to be more specific for osteoid osteoma.

Osteoid Osteoma Facts

• Bengin neoplasm of osteoid and woven bone, 90% occur 5-25 yo
• Classic Hx “Pain worse at night, relieved by aspirin…”
• Location metadiaphysis of long bones (73%), 10-14% in spine
• Types:
  
  • Cortical (=nidus in cortex) has solid laminated periosteal reaction radiolucent center (nidus) ± central osteosclerosis
  • Cancellous (=intramedullary) intraarticular lesion, difficult to identify, little osteosclerosis, widened joint space
  • Subperiosteal (rare) round soft-tissue mass adjacent to bone