Abnormality is centred at C4/5 level, with bone marrow enhancement that extends through the right articular pillar, pedicle and right side of vertebral body at C4 and C5. CT confirms fusion of the right C4/5 facet joint, with an irregular calcific focus at the posterior aspect of the adjacent exit foramen, and lucency with cortical loss where the involved articular pillar forms the posterior margin of the exit foramen.
Gross soft tissue oedema within the surrounding paravertebral muscles with extension towards the midline anteriorly and posteriorly. No rim enhancing paravertebral fluid collection.
The oldest imaging available for comparison, the MRI from 2011, suggests a fracture fragment at the C5 superior articular process, with no MR evidence of fusion across the C4/5 facet at that time.
The remainder of the cervical spine demonstrates normal marrow signal. No canal stenosis or cord signal abnormality.
Conclusion :
Evidence of previous trauma in the right C4/5 articular pillar. Focus of ossification in the posterior aspect of the right exit foramen with associated florid surrounding soft tissue and bone marrow enhancement which has an appearance consistent with inflammation rather than tumour. Given previous history, this is most likely represent myositis ossificans. A less likely possibility would be post-traumatic degeneration with chronic indolent infection.