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Os Odontoideum
Kevin R. Moore, MD
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KEY FACTS

  • Terminology

    • Imaging

      • Top Differential Diagnoses

        • Pathology

          • Clinical Issues

            • Diagnostic Checklist

              TERMINOLOGY

              • Synonyms

                • Os
              • Definitions

                • Corticated oval or round ossicle (os) at odontoid process tip
                • 2 types described based on position of os
                  • Orthotopic: Os in normal position of odontoid tip
                  • Dystopic: Os in any other location
                    • Most commonly os located near foramen magnum, may fuse with clivus (os avis) or anterior C1 ring

              IMAGING

              • General Features

                • Radiographic Findings

                  • CT Findings

                    • MR Findings

                      • Imaging Recommendations

                        DIFFERENTIAL DIAGNOSIS

                          PATHOLOGY

                          • General Features

                            • Staging, Grading, & Classification

                              • Gross Pathologic & Surgical Features

                                CLINICAL ISSUES

                                • Presentation

                                  • Demographics

                                    • Natural History & Prognosis

                                      • Treatment

                                        DIAGNOSTIC CHECKLIST

                                        • Consider

                                          Selected References

                                          1. White D et al: The role of conservative management in incidental os odontoideum. World Neurosurg. 88:695.e15-7, 2016
                                          2. Akpolat YT et al: Treatment of os odontoideum in a patient with spastic quadriplegic cerebral palsy. J Clin Neurosci. 22(8):1239-43, 2015
                                          3. Nguyen JC et al: Os odontoideum. Pediatr Emerg Care. 31(3):225-7, 2015
                                          4. O'Brien WT Sr et al: The dens: normal development, developmental variants and anomalies, and traumatic injuries. J Clin Imaging Sci. 5:38, 2015
                                          5. Rahimizadeh A et al: Atlantoaxial subluxation due to an os odontoideum in an achondroplastic adult: report of a case and review of the literature. Case Rep Orthop. 2015:142586, 2015
                                          6. Pang D et al: Embryology and bony malformations of the craniovertebral junction. Childs Nerv Syst. 27(4):523-64, 2011
                                          7. Arvin B et al: Os odontoideum: etiology and surgical management. Neurosurgery. 66(3 Suppl):22-31, 2010
                                          8. Visocchi M et al: Reducible and irreducible os odontoideum in childhood treated with posterior wiring, instrumentation and fusion. Past or present? Acta Neurochir (Wien). 151(10):1265-74, 2009
                                          9. Wada E et al: Os odontoideum as a consequence of a posttraumatic displaced ossiculum terminale. A case report. J Bone Joint Surg Am. 91(7):1750-4, 2009
                                          10. Klimo P Jr et al: Os odontoideum: presentation, diagnosis, and treatment in a series of 78 patients. J Neurosurg Spine. 9(4):332-42, 2008
                                          11. Menezes AH et al: Anatomy and biomechanics of normal craniovertebral junction (a) and biomechanics of stabilization (b). Childs Nerv Syst. 24(10):1091-100, 2008
                                          12. Menezes AH: Craniocervical developmental anatomy and its implications. Childs Nerv Syst. 24(10):1109-22, 2008
                                          13. Menezes AH: Craniovertebral junction database analysis: incidence, classification, presentation, and treatment algorithms. Childs Nerv Syst. 24(10):1101-8, 2008
                                          14. Smoker WR et al: Imaging the craniocervical junction. Childs Nerv Syst. 24(10):1123-45, 2008
                                          15. Gupta V et al: Dynamic magnetic resonance imaging evaluation of craniovertebral junction abnormalities. J Comput Assist Tomogr. 31(3):354-9, 2007
                                          16. Klimo P Jr et al: Congenital anomalies of the cervical spine. Neurosurg Clin N Am. 18(3):463-78, 2007
                                          17. Choit RL et al: Os odontoideum: a significant radiographic finding. Pediatr Radiol. 35(8):803-7, 2005
                                          18. Vargas TM et al: Atlantoaxial instability associated with an orthotopic os odontoideum: a multimodality imaging assessment. Emerg Radiol. 11(4):223-5, 2005
                                          Related Anatomy
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                                          Related Differential Diagnoses
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                                          References
                                          Tables

                                          Tables

                                          KEY FACTS

                                          • Terminology

                                            • Imaging

                                              • Top Differential Diagnoses

                                                • Pathology

                                                  • Clinical Issues

                                                    • Diagnostic Checklist

                                                      TERMINOLOGY

                                                      • Synonyms

                                                        • Os
                                                      • Definitions

                                                        • Corticated oval or round ossicle (os) at odontoid process tip
                                                        • 2 types described based on position of os
                                                          • Orthotopic: Os in normal position of odontoid tip
                                                          • Dystopic: Os in any other location
                                                            • Most commonly os located near foramen magnum, may fuse with clivus (os avis) or anterior C1 ring

                                                      IMAGING

                                                      • General Features

                                                        • Radiographic Findings

                                                          • CT Findings

                                                            • MR Findings

                                                              • Imaging Recommendations

                                                                DIFFERENTIAL DIAGNOSIS

                                                                  PATHOLOGY

                                                                  • General Features

                                                                    • Staging, Grading, & Classification

                                                                      • Gross Pathologic & Surgical Features

                                                                        CLINICAL ISSUES

                                                                        • Presentation

                                                                          • Demographics

                                                                            • Natural History & Prognosis

                                                                              • Treatment

                                                                                DIAGNOSTIC CHECKLIST

                                                                                • Consider

                                                                                  Selected References

                                                                                  1. White D et al: The role of conservative management in incidental os odontoideum. World Neurosurg. 88:695.e15-7, 2016
                                                                                  2. Akpolat YT et al: Treatment of os odontoideum in a patient with spastic quadriplegic cerebral palsy. J Clin Neurosci. 22(8):1239-43, 2015
                                                                                  3. Nguyen JC et al: Os odontoideum. Pediatr Emerg Care. 31(3):225-7, 2015
                                                                                  4. O'Brien WT Sr et al: The dens: normal development, developmental variants and anomalies, and traumatic injuries. J Clin Imaging Sci. 5:38, 2015
                                                                                  5. Rahimizadeh A et al: Atlantoaxial subluxation due to an os odontoideum in an achondroplastic adult: report of a case and review of the literature. Case Rep Orthop. 2015:142586, 2015
                                                                                  6. Pang D et al: Embryology and bony malformations of the craniovertebral junction. Childs Nerv Syst. 27(4):523-64, 2011
                                                                                  7. Arvin B et al: Os odontoideum: etiology and surgical management. Neurosurgery. 66(3 Suppl):22-31, 2010
                                                                                  8. Visocchi M et al: Reducible and irreducible os odontoideum in childhood treated with posterior wiring, instrumentation and fusion. Past or present? Acta Neurochir (Wien). 151(10):1265-74, 2009
                                                                                  9. Wada E et al: Os odontoideum as a consequence of a posttraumatic displaced ossiculum terminale. A case report. J Bone Joint Surg Am. 91(7):1750-4, 2009
                                                                                  10. Klimo P Jr et al: Os odontoideum: presentation, diagnosis, and treatment in a series of 78 patients. J Neurosurg Spine. 9(4):332-42, 2008
                                                                                  11. Menezes AH et al: Anatomy and biomechanics of normal craniovertebral junction (a) and biomechanics of stabilization (b). Childs Nerv Syst. 24(10):1091-100, 2008
                                                                                  12. Menezes AH: Craniocervical developmental anatomy and its implications. Childs Nerv Syst. 24(10):1109-22, 2008
                                                                                  13. Menezes AH: Craniovertebral junction database analysis: incidence, classification, presentation, and treatment algorithms. Childs Nerv Syst. 24(10):1101-8, 2008
                                                                                  14. Smoker WR et al: Imaging the craniocervical junction. Childs Nerv Syst. 24(10):1123-45, 2008
                                                                                  15. Gupta V et al: Dynamic magnetic resonance imaging evaluation of craniovertebral junction abnormalities. J Comput Assist Tomogr. 31(3):354-9, 2007
                                                                                  16. Klimo P Jr et al: Congenital anomalies of the cervical spine. Neurosurg Clin N Am. 18(3):463-78, 2007
                                                                                  17. Choit RL et al: Os odontoideum: a significant radiographic finding. Pediatr Radiol. 35(8):803-7, 2005
                                                                                  18. Vargas TM et al: Atlantoaxial instability associated with an orthotopic os odontoideum: a multimodality imaging assessment. Emerg Radiol. 11(4):223-5, 2005