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Retroodontoid Pseudotumor
Jeffrey S. Ross, MD
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KEY FACTS

  • Terminology

    • Imaging

      • Top Differential Diagnoses

        • Clinical Issues

          • Diagnostic Checklist

            TERMINOLOGY

            • Synonyms

              • Periodontoid pseudotumor
            • Definitions

              • Nonneoplastic low T2 signal mass posterior to odontoid process related to rheumatoid arthritis (RA), degenerative change with chronic abnormal motion, and atlantoaxial subluxation, without significant calcification
              • Not to be confused with
                • Crowned dens syndrome: Fever with cervicooccipital junction pain, stiffness with associated calcification of transverse ligament, and nonenhancing retroodontoid soft tissue; associated with calcium pyrophosphate dihydrate crystal deposition disease (CPPD) or hydroxyapatite deposition
                • Pseudogout: Arthritis caused by CPPD crystal inflammation with symptoms like gout
                • Tophaceous pseudogout: Large accumulation of material giving pattern of soft tissue tumor with mass effect/cord compression
                • RA soft tissue posterior to odontoid referred to as pannus

            IMAGING

            • General Features

              • CT Findings

                • MR Findings

                  • Imaging Recommendations

                    DIFFERENTIAL DIAGNOSIS

                      PATHOLOGY

                      • General Features

                        • Gross Pathologic & Surgical Features

                          CLINICAL ISSUES

                          • Presentation

                            • Demographics

                              • Natural History & Prognosis

                                • Treatment

                                  DIAGNOSTIC CHECKLIST

                                  • Consider

                                    • Image Interpretation Pearls

                                      • Reporting Tips

                                        Selected References

                                        1. Shi J et al: Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies. Skeletal Radiol. 48(10):1511-23, 2019
                                        2. Yu SH et al: Retro-odontoid pseudotumor without atlantoaxial subluxation or rheumatic arthritis. Korean J Neurotrauma. 12(2):180-4, 2016
                                        3. Ea HK et al: Diagnosis and clinical manifestations of calcium pyrophosphate and basic calcium phosphate crystal deposition diseases. Rheum Dis Clin North Am. 40(2):207-29, 2014
                                        4. Chang EY et al: Frequency of atlantoaxial calcium pyrophosphate dihydrate deposition at CT. Radiology. 269(2):519-24, 2013
                                        5. Mwaka ES et al: Calcium pyrophosphate dehydrate crystal deposition in the ligamentum flavum of the cervical spine: histopathological and immunohistochemical findings. Clin Exp Rheumatol. 27(3):430-8, 2009
                                        6. Taniguchi A et al: Painful neck on rotation: diagnostic significance for crowned dens syndrome. J Neurol. 257(1):132-5, 2009
                                        7. Fenoy AJ et al: Calcium pyrophosphate dihydrate crystal deposition in the craniovertebral junction. J Neurosurg Spine. 8(1):22-9, 2008
                                        8. Salaffi F et al: The crowned dens syndrome as a cause of neck pain: clinical and computed tomography study in patients with calcium pyrophosphate dihydrate deposition disease. Clin Exp Rheumatol. 26(6):1040-6, 2008
                                        9. Doita M et al: Calcium pyrophosphate dihydrate deposition in the transverse ligament of the atlas: an unusual cause of cervical myelopathy. Skeletal Radiol. 36(7):699-702, 2007
                                        10. Goto S et al: Crowned Dens syndrome. J Bone Joint Surg Am. 89(12):2732-6, 2007
                                        11. Feydy A et al: Cervical spine and crystal-associated diseases: imaging findings. Eur Radiol. 16(2):459-68, 2006
                                        12. Lin SH et al: Cervical myelopathy induced by pseudogout in ligamentum flavum and retro-odontoid mass: a case report. Spinal Cord. 44(11):692-4, 2006
                                        13. Finckh A et al: The cervical spine in calcium pyrophosphate dihydrate deposition disease. A prevalent case-control study. J Rheumatol. 31(3):545-9, 2004
                                        14. Muthukumar N et al: Tumoral calcium pyrophosphate dihydrate deposition disease of the ligamentum flavum. Neurosurgery. 53(1):103-8; discussion 108-9, 2003
                                        15. Assaker R et al: Foramen magnum syndrome secondary to calcium pyrophosphate crystal deposition in the transverse ligament of the atlas. Spine (Phila Pa 1976). 26(12):1396-400, 2001
                                        16. Baysal T et al: The crowned dens syndrome: a rare form of calcium pyrophosphate deposition disease. Eur Radiol. 10(6):1003-5, 2000
                                        17. Kakitsubata Y et al: Calcium pyrophosphate dihydrate crystal deposition in and around the atlantoaxial joint: association with type 2 odontoid fractures in nine patients. Radiology. 216(1):213-9, 2000
                                        18. Fye KH et al: Compressive cervical myelopathy due to calcium pyrophosphate dihydrate deposition disease: report of a case and review of the literature. Arch Intern Med. 159(2):189-93, 1999
                                        19. Resnick D et al: Vertebral involvement in calcium pyrophosphate dihydrate crystal deposition disease. Radiographic-pathological correlation. Radiology. 153(1):55-60, 1984
                                        Related Anatomy
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                                        Related Differential Diagnoses
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                                        References
                                        Tables

                                        Tables

                                        KEY FACTS

                                        • Terminology

                                          • Imaging

                                            • Top Differential Diagnoses

                                              • Clinical Issues

                                                • Diagnostic Checklist

                                                  TERMINOLOGY

                                                  • Synonyms

                                                    • Periodontoid pseudotumor
                                                  • Definitions

                                                    • Nonneoplastic low T2 signal mass posterior to odontoid process related to rheumatoid arthritis (RA), degenerative change with chronic abnormal motion, and atlantoaxial subluxation, without significant calcification
                                                    • Not to be confused with
                                                      • Crowned dens syndrome: Fever with cervicooccipital junction pain, stiffness with associated calcification of transverse ligament, and nonenhancing retroodontoid soft tissue; associated with calcium pyrophosphate dihydrate crystal deposition disease (CPPD) or hydroxyapatite deposition
                                                      • Pseudogout: Arthritis caused by CPPD crystal inflammation with symptoms like gout
                                                      • Tophaceous pseudogout: Large accumulation of material giving pattern of soft tissue tumor with mass effect/cord compression
                                                      • RA soft tissue posterior to odontoid referred to as pannus

                                                  IMAGING

                                                  • General Features

                                                    • CT Findings

                                                      • MR Findings

                                                        • Imaging Recommendations

                                                          DIFFERENTIAL DIAGNOSIS

                                                            PATHOLOGY

                                                            • General Features

                                                              • Gross Pathologic & Surgical Features

                                                                CLINICAL ISSUES

                                                                • Presentation

                                                                  • Demographics

                                                                    • Natural History & Prognosis

                                                                      • Treatment

                                                                        DIAGNOSTIC CHECKLIST

                                                                        • Consider

                                                                          • Image Interpretation Pearls

                                                                            • Reporting Tips

                                                                              Selected References

                                                                              1. Shi J et al: Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies. Skeletal Radiol. 48(10):1511-23, 2019
                                                                              2. Yu SH et al: Retro-odontoid pseudotumor without atlantoaxial subluxation or rheumatic arthritis. Korean J Neurotrauma. 12(2):180-4, 2016
                                                                              3. Ea HK et al: Diagnosis and clinical manifestations of calcium pyrophosphate and basic calcium phosphate crystal deposition diseases. Rheum Dis Clin North Am. 40(2):207-29, 2014
                                                                              4. Chang EY et al: Frequency of atlantoaxial calcium pyrophosphate dihydrate deposition at CT. Radiology. 269(2):519-24, 2013
                                                                              5. Mwaka ES et al: Calcium pyrophosphate dehydrate crystal deposition in the ligamentum flavum of the cervical spine: histopathological and immunohistochemical findings. Clin Exp Rheumatol. 27(3):430-8, 2009
                                                                              6. Taniguchi A et al: Painful neck on rotation: diagnostic significance for crowned dens syndrome. J Neurol. 257(1):132-5, 2009
                                                                              7. Fenoy AJ et al: Calcium pyrophosphate dihydrate crystal deposition in the craniovertebral junction. J Neurosurg Spine. 8(1):22-9, 2008
                                                                              8. Salaffi F et al: The crowned dens syndrome as a cause of neck pain: clinical and computed tomography study in patients with calcium pyrophosphate dihydrate deposition disease. Clin Exp Rheumatol. 26(6):1040-6, 2008
                                                                              9. Doita M et al: Calcium pyrophosphate dihydrate deposition in the transverse ligament of the atlas: an unusual cause of cervical myelopathy. Skeletal Radiol. 36(7):699-702, 2007
                                                                              10. Goto S et al: Crowned Dens syndrome. J Bone Joint Surg Am. 89(12):2732-6, 2007
                                                                              11. Feydy A et al: Cervical spine and crystal-associated diseases: imaging findings. Eur Radiol. 16(2):459-68, 2006
                                                                              12. Lin SH et al: Cervical myelopathy induced by pseudogout in ligamentum flavum and retro-odontoid mass: a case report. Spinal Cord. 44(11):692-4, 2006
                                                                              13. Finckh A et al: The cervical spine in calcium pyrophosphate dihydrate deposition disease. A prevalent case-control study. J Rheumatol. 31(3):545-9, 2004
                                                                              14. Muthukumar N et al: Tumoral calcium pyrophosphate dihydrate deposition disease of the ligamentum flavum. Neurosurgery. 53(1):103-8; discussion 108-9, 2003
                                                                              15. Assaker R et al: Foramen magnum syndrome secondary to calcium pyrophosphate crystal deposition in the transverse ligament of the atlas. Spine (Phila Pa 1976). 26(12):1396-400, 2001
                                                                              16. Baysal T et al: The crowned dens syndrome: a rare form of calcium pyrophosphate deposition disease. Eur Radiol. 10(6):1003-5, 2000
                                                                              17. Kakitsubata Y et al: Calcium pyrophosphate dihydrate crystal deposition in and around the atlantoaxial joint: association with type 2 odontoid fractures in nine patients. Radiology. 216(1):213-9, 2000
                                                                              18. Fye KH et al: Compressive cervical myelopathy due to calcium pyrophosphate dihydrate deposition disease: report of a case and review of the literature. Arch Intern Med. 159(2):189-93, 1999
                                                                              19. Resnick D et al: Vertebral involvement in calcium pyrophosphate dihydrate crystal deposition disease. Radiographic-pathological correlation. Radiology. 153(1):55-60, 1984