Os Terminale - Os Odontoideum Complex (2)

Sagittal reformatted CT image shows an os terminale, sitting on top of the normal-sized dens.

Os Terminale

• Derived from the 4th occipital sclerotome but does not undergo fusion with the dens
• The dens is normal in size and shape
• If it enlarges, coupled with dens hypoplasia -- it is called os odontoideum
• Usually single, smooth
• Sometimes can show bony fragmentation mimicking a comminuted fracture (but one should be aware that an extensively comminuted fracture at the tip of the dens is extremely rare or nonexistent)

Reference:

Swischuk L. Imaging of the cervical spine in children, 2004.