Diagnosis & Imaging
Retroflexed odontoid
A retroflexed odontoid is a backward-tilted odontoid process that can compress the front of the brainstem, a feature of complex Chiari malformation.
In short: Retroflexed odontoid
- It is a backward tilt of the odontoid process.
- It can compress the front (ventral surface) of the brainstem.
- It is a feature of complex Chiari malformation.
- It can require additional surgery beyond decompression.
What it is
A retroflexed odontoid is an odontoid process (the tooth-like projection of the second vertebra) that is tilted backward. This backward tilt can compress the front (ventral surface) of the brainstem, and it is a recognized feature of complex Chiari malformation.
Understanding Retroflexed odontoid
When the odontoid tilts backward (retroflexes), its upper portion projects toward the brainstem, potentially compressing it from the front. This ventral (front-side) brainstem compression can contribute to symptoms and is one of the bony abnormalities defining complex Chiari. Its presence is significant because relieving it may require more than standard posterior decompression — sometimes including procedures to address the front-side compression (such as odontoidectomy) and craniocervical fusion for stability. The degree of ventral compression is assessed with craniometric measurements (such as the pB-C2 line and clivo-axial angle). Recognizing a retroflexed odontoid ensures the full craniocervical picture is addressed. Understanding the retroflexed odontoid clarifies a bony feature causing front-side brainstem compression in complex Chiari.
Why it matters
Understanding the retroflexed odontoid helps families see how a backward-tilted odontoid can compress the front of the brainstem in complex Chiari, and why this can require additional surgery beyond standard decompression.
Common questions
What is a retroflexed odontoid?
A backward-tilted odontoid process.
What does it do?
It can compress the front of the brainstem.
Why does it matter?
It is a feature of complex Chiari that can require additional surgery.
Bottom line
A retroflexed odontoid is a backward-tilted odontoid that can compress the front of the brainstem, a feature of complex Chiari that may require additional surgery.
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