Persistent ossiculum terminale

Last revised by Mohd Ashyiraff Ilani Bin Ismail on 28 Nov 2024

The ossiculum terminale appears as a secondary ossification center of the dens between 3-6 years and normally fuses by 12 years. Failure of fusion results in a persistent ossiculum terminale (also called Bergmann's ossicle or ossiculum terminale of Bergmann) and is considered a normal anatomical variant of the axis. It is important not to misinterpret this anatomical variant with dens fracture.

It lies above the alar ligament and is therefore considered to be stable and it very rarely causes symptoms.

Radiographic features

  • small, well-corticated ossicle at the tip of the dens

  • usually in the midline

  • dens is typically normal in height 4

Differential diagnosis