Odontoid process agenesis

Last revised by Joshua Yap ◉ on 4 Apr 2023

Citation, DOI, disclosures and article data

Citation:

Iqbal S, Yap J, azimi m, et al. Odontoid process agenesis. Reference article, Radiopaedia.org (Accessed on 30 Sep 2023) https://doi.org/10.53347/rID-87627

DOI:

https://doi.org/10.53347/rID-87627

Permalink:

https://radiopaedia.org/articles/87627

rID:

87627

Article created:

10 Mar 2021, Subhan Iqbal

Disclosures:

At the time the article was created Subhan Iqbal had no recorded disclosures.

View Subhan Iqbal's current disclosures

Last revised:

4 Apr 2023, Joshua Yap ◉

Disclosures:

At the time the article was last revised Joshua Yap had no financial relationships to ineligible companies to disclose.

View Joshua Yap's current disclosures

Revisions:

11 times, by 4 contributors - see full revision history and disclosures

Systems:

Paediatrics, Spine, Musculoskeletal

Sections:

Anatomy

Odontoid process agenesis is rare, occurring due to a lack of failure of ossification of the odontoid process. It is seen in patients with spondyloepiphyseal and spondylometaphyseal dysplasia ^1,2.

Radiographic features

Plain radiograph

On plain film, odontoid process agenesis appears as a slight depression between the superior articular facets on open mouth view, or hypogenesis of the basal segment of the odontoid with a floating apical process. Both of these conditions are associated with atlantoaxial instability.

CT

On dynamic CT, both flexion and extension views should be performed to identify posterior subluxation.

Treatment and prognosis

Atlantoaxial instability will lead to vascular compression and stroke because of ischemia ^2,4. Treatment options include surgical fusion of C1 and C2.