Occipital Vertebra

Description

Pre-basioccipital arch (thin arrows), a U-shaped bony valance on the ventral lip of the anterior foramen magnum rim. This results from complete preservation of the hypochordal bow of the proatlas

Name

• Occipital Vertebra

General

• Rare anatomic variants of the occipital bone
• There is a broad spectrum of variants, the more common ones are included
• One of the accessory bones of the spine

Radiographic Findings

• Best detected on CT, which can help differentiate them from fractures

Paramastoid Process

• Best viewed on coronal CT
• Broad, bony protuberance arising from the inferior aspect of the jugular process of the occiput

Basilar Process

• Small bony protuberance on the inferior surface of the clivus, anterior rim of foramen magnum
• Found between the occipital condyles in a slightly paramedian location

Prebasioccipital Arch

• U shaped bone arch arising from the inferior surface of the clivus
• It is draped across the anterior rim of the foramen magnum between the tips of the occipital condyles

Third Condyle

• Appears as a midline bony protuberance at the base of the clivus, anterior to foramen magnum
• May exist as an isolated accessory ossicle or be fused to the occiput

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Clinical Significance

• Clinical significance is not well understood or described

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See Also

• Accessory Bones Main
• HEENT Anatomy Main

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