Retroodontoid Pseudotumor Related to Development of Myelopathy Secondary to Atlantoaxial Instability on Os Odontoideum

Clinical and MR Predictors of Retro-Odontoid Pseudotumor Regression Following Posterior Fixation in Patients with Atlantoaxial Instability

Purpose

To identify clinical and MR predictors of retro-odontoid pseudotumor (ROP) regression after posterior fixation in patients with atlantoaxial instability.

Materials and Methods

We included patients who had undergone posterior fixation for atlantoaxial instability and preoperative and postoperative MR imaging. Patients were classified into two groups according to the degree of ROP regression after posterior fixation: regression (≥ 10% reduction) and no regression (< 10% reduction). Mann-Whitney and Fisher's exact tests were performed to identify the clinical (age and sex) and MR predictors (preoperative ROP thickness, ROP type, MR signal homogeneity of the ROP, spinal cord signal change, spinal cord atrophy, ossified posterior longitudinal ligament, os odontoideum, and atlantodental interval) associated with ROP regression.

Results

We retrospectively assessed 11 consecutive patients (7 female; median age, 66 years [range, 31-84 years]). Posterior fixation induced ROP regression in eight (72.7%) patients. Older age and greater preoperative ROP thickness significantly correlated with ROP regression (p = 0.024 and 0.012, respectively). All patients with preoperative ROP thickness > 5 mm exhibited ROP regression. The other variables were not significantly associated with ROP regression.

Conclusion

Older age and thicker preoperative ROP are associated with ROP regression after posterior fixation in patients with atlantoaxial instability.

Retro-odontoid pseudotumor with uncommon presentation of cervical spine injury

Background

We report the first case of retro‐odontoid pseudotumor with an isolated symptom of C2–C3 dysesthesia triggered by a traumatic event.

Case Presentation

An 86‐year‐old man, who was a wood craftsman for more than 50 years, presented to the emergency room with sudden‐onset severe posterior head and neck dysesthesia after accidentally falling backward. No neurological impairment of the extremities was noted. Computed tomography revealed a C2–C7 osteophyte formation, mainly in front of the vertebral bodies. Moreover, magnetic resonance imaging showed cervical spinal cord compression by a soft tissue mass posterior to the odontoid process of the axis. Therefore, we diagnosed a cervical spine injury with an isolated symptom of C2–C3 dysesthesia due to a retro‐odontoid pseudotumor. He did not undergo surgical intervention and was transferred to a rehabilitation hospital on day 11 for pain control.

Conclusion

Our report could be useful to emergency physicians dealing with similar cases of cervical symptoms following trauma.

Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies

Retro-odontoid pseudotumor, or mass-like retro-odontoid soft tissue thickening, is an uncommon but important imaging finding that may be associated with rheumatoid arthritis, crystal deposition diseases, as well as non-inflammatory conditions such as cervical degenerative changes and mechanical alterations. Retro-odontoid pseudotumor is commonly associated with atlantoaxial microinstability or subluxation. MRI and CT have an important role in the detection and diagnosis of retro-odontoid pseudotumor. However, due to a wide range of imaging characteristics and ambiguous etiology, it is a frequently misunderstood entity. The purpose of this article is to review relevant anatomy of the craniocervical junction; describe various imaging appearances, pathophysiology and histology in both rheumatoid and non-rheumatoid etiologies; and discuss differential diagnosis of retro-odontoid pseudotumor in order to help guide clinical management.