Corticated, oval or round 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
Goel A et al: Os odontoideum: analysis of 190 surgically treated cases. World Neurosurg. 134:e512-23, 2020
Helenius IJ et al: Os odontoideum in children: treatment outcomes and neurological risk factors. J Bone Joint Surg Am. 101(19):1750-60, 2019
Sato H et al: Familial Os odontoideum: proatlas segmentation abnormality. World Neurosurg. 130:146-9, 2019
Buyukkaya A et al: Characteristic imaging findings of os odontoideum. Spine J. 14(12):3052-3, 2014
Kulkarni GB et al: Profile oF patients with craniovertebral junction anomalies with posterior circulation strokes. J Stroke Cerebrovasc Dis. 23(10):2819-26, 2014
Visocchi M et al: Os odontoideum syndrome: pathogenesis, clinical patterns and indication for surgical strategies in childhood. Adv Tech Stand Neurosurg. 40:273-93, 2014
Pang D et al: Embryology and bony malformations of the craniovertebral junction. Childs Nerv Syst. 27(4):523-64, 2011
Arvin B et al: Os odontoideum: etiology and surgical management. Neurosurgery. 66(3 Suppl):22-31, 2010
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
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
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
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
Menezes AH: Craniocervical developmental anatomy and its implications. Childs Nerv Syst. 24(10):1109-22, 2008
Menezes AH: Craniovertebral junction database analysis: incidence, classification, presentation, and treatment algorithms. Childs Nerv Syst. 24(10):1101-8, 2008
Smoker WR et al: Imaging the craniocervical junction. Childs Nerv Syst. 24(10):1123-45, 2008
Gupta V et al: Dynamic magnetic resonance imaging evaluation of craniovertebral junction abnormalities. J Comput Assist Tomogr. 31(3):354-9, 2007
Klimo P Jr et al: Congenital anomalies of the cervical spine. Neurosurg Clin N Am. 18(3):463-78, 2007
Choit RL et al: Os odontoideum: a significant radiographic finding. Pediatr Radiol. 35(8):803-7, 2005
Vargas TM et al: Atlantoaxial instability associated with an orthotopic os odontoideum: a multimodality imaging assessment. Emerg Radiol. 11(4):223-5, 2005
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References
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Tables
KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
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Diagnostic Checklist
TERMINOLOGY
Synonyms
Ossicle (Os)
Definitions
Corticated, oval or round 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
Goel A et al: Os odontoideum: analysis of 190 surgically treated cases. World Neurosurg. 134:e512-23, 2020
Helenius IJ et al: Os odontoideum in children: treatment outcomes and neurological risk factors. J Bone Joint Surg Am. 101(19):1750-60, 2019
Sato H et al: Familial Os odontoideum: proatlas segmentation abnormality. World Neurosurg. 130:146-9, 2019
Buyukkaya A et al: Characteristic imaging findings of os odontoideum. Spine J. 14(12):3052-3, 2014
Kulkarni GB et al: Profile oF patients with craniovertebral junction anomalies with posterior circulation strokes. J Stroke Cerebrovasc Dis. 23(10):2819-26, 2014
Visocchi M et al: Os odontoideum syndrome: pathogenesis, clinical patterns and indication for surgical strategies in childhood. Adv Tech Stand Neurosurg. 40:273-93, 2014
Pang D et al: Embryology and bony malformations of the craniovertebral junction. Childs Nerv Syst. 27(4):523-64, 2011
Arvin B et al: Os odontoideum: etiology and surgical management. Neurosurgery. 66(3 Suppl):22-31, 2010
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
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
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
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
Menezes AH: Craniocervical developmental anatomy and its implications. Childs Nerv Syst. 24(10):1109-22, 2008
Menezes AH: Craniovertebral junction database analysis: incidence, classification, presentation, and treatment algorithms. Childs Nerv Syst. 24(10):1101-8, 2008
Smoker WR et al: Imaging the craniocervical junction. Childs Nerv Syst. 24(10):1123-45, 2008
Gupta V et al: Dynamic magnetic resonance imaging evaluation of craniovertebral junction abnormalities. J Comput Assist Tomogr. 31(3):354-9, 2007
Klimo P Jr et al: Congenital anomalies of the cervical spine. Neurosurg Clin N Am. 18(3):463-78, 2007
Choit RL et al: Os odontoideum: a significant radiographic finding. Pediatr Radiol. 35(8):803-7, 2005
Vargas TM et al: Atlantoaxial instability associated with an orthotopic os odontoideum: a multimodality imaging assessment. Emerg Radiol. 11(4):223-5, 2005
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