What is the differential diagnosis for the appearance of the dens?
Os ondontoideum, persistent ossiculum terminale, type 1 dens fracture.
What features support the diagnosis of persistent ossiculum terminale?
Small (os odontoideum is larger) with well-corticated, regular margins (type 1 dens fractures tend to have irregular, non-corticated margins).
What age does the ossiculum terminale appear and what age does it normally ossify?
Appears at 5-6 years of age and usually fuses by age 12.
Well-corticated bony fragment superior to the dens most likely represents a persistent ossiculum terminale.
Multilevel degenerative disease most severe at C5/6 and C6/7 with loss of intervertebral disc space height and partial fusion of C6 and C7 vertebral bodies. Minimal anterolisthesis C4 on C5 is almost certainly a result. Anterolateral osteophytes from C3-C7 with multiple lucencies that appear well corticated and are not acute fractures. Moderate facet joint arthropathy. Rounded lucency in the right C5 articular process has a slightly unusual appearance that may reflect a subchondral cyst/geode or an haemangioma, although more aggressive lesions cannot be excluded on this study.
No acute cervical spine fracture or malalignment demonstrated. Prevertebral soft tissues are within normal limits.