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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.

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Correspondence to Junzi Shi.

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Shi, J., Ermann, J., Weissman, B.N. et al. Thinking beyond pannus: a review of retro-odontoid pseudotumor due to rheumatoid and non-rheumatoid etiologies. Skeletal Radiol 48, 1511–1523 (2019).

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  • Atlantoaxial
  • Cervical spine
  • Odontoid
  • Pannus
  • Retro-odontoid pseudotumor
  • Rheumatoid arthritis