Chance findings in a 57 year old male. In the axial slice a joint space can be seen on the right side (“C2-3 joint”). On the left side an enlarged well defined round opacity can be seen with variable internal density – yellow arrow (“C2-3 joint fused”). This is primary congenital fusion of the joint C2-3 with consequent degenerative process with hyperostosis. There is also hypogenesis of the left C1-2 joint – large space between C2 lateral pedicle marked by red arrow (“C1-2 hypogenesis”). Look at the right side to see a normal C1-2 joint. The C2-3 enlargement reflects advanced degeneration in course of congenital deformities (secondary to chronic change of the physiological function).
Any CBCT with an abnormality like this should be referred for confirmation that this is a benign finding.