✓ Retroodontoid or periodontoid pseudotumor unassociated with rheumatoid arthritis or hemodialysis is clinically rare. The authors report three cases of retroodontoid pseudotumor that they treated surgically. All patients exhibited myelopathy of the upper cervical spinal cord. Plain radiography depicted atlantoaxial instability in two of the three patients. Spinal cord compression caused by a mass lesion in all patients was clearly demonstrated on magnetic resonance images. In two patients, the mass lesion was not limited to the retroodontoid region and expanded continuously to the cranial base. Posterior laminectomy of the atlas and occipitocervical fusion were performed. After surgery, the pseudotumor disappeared in two cases and was clearly reduced in one case, and neurological symptoms also improved. Retroodontoid pseudotumor is a lesion for which symptomatic improvement can be expected with posterior decompression and fusion, even without direct tumor excision.
Abbreviations used in this paper:ADI = atlas–dens interval; CRP = C-reactive protein; JOA = Japanese Orthopaedic Association; MR = magnetic resonance; WBC = white blood cell.
Address reprint requests to: Sei Shibuya, M.D., Ph.D., Department of Orthopaedic Surgery, Kagawa University School of Medicine, 1750-1 Ikenobe, Miki-cho, Kagawa 761-0793, Japan. email:
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