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Factors Influencing on Retro-Odontoid Soft-Tissue Thickness: Analysis by Magnetic Resonance Imaging

Tojo, Shinjiro, MD; Kawakami, Reina, MD; Yonenaga, Takenori, MD; Hayashi, Daichi, MD; Fukuda, Kunihiko, MD, PhD

doi: 10.1097/BRS.0b013e3182715c07

Study Design. A retrospective, consecutive case series.

Objective. To analyze the relationship between retro-odontoid soft-tissue thickness and patients' age, sex, and degenerative changes of cervical spine and to investigate the effect these factors have on retro-odontoid soft-tissue thickness.

Summary of Background Data. Thickening of the soft tissue posterior to the odontoid process can form a retro-odontoid pseudotumor causing symptoms of spinal cord compression. Rheumatoid arthritis and long-term dialysis have been reported as possible causes for this. However, there have been reports of retro-odontoid pseudotumors without coexisting diseases.

Methods. Findings from a total of 503 cases of cervical spine magnetic resonance images were reviewed, and retro-odontoid soft-tissue thickness was measured. The values were matched for age, sex, presence of degenerative changes, rheumatoid arthritis, and dialysis and were analyzed for significance.

Results. Retro-odontoid soft tissue thickened with age, and this was also seen in male patients and patients with degenerative changes. Significant increase in thickness was also observed in patients undergoing dialysis and further increased with prolonged dialysis. There was no significant association with presence of rheumatoid arthritis.

Conclusion. There is association between age, sex, degenerative cervical spine changes, and dialysis with retro-odontoid soft-tissue thickness. With dialysis, retro-odontoid soft-tissue thickness increases with increasing duration. Thus, reviewing magnetic resonance image from daily practice indicates that cervical spine degeneration is associated with the development of retro-odontoid pseudotumors.

We discussed the factors causing retro-odontoid soft-tissue thickening by measuring the thickness of retro-odontoid soft tissue in cervical magnetic resonance images of 503 consecutive cases retrospectively. We found that aging, sex, cervical spondylosis, and dialysis history can be factors causing retro-odontoid soft-tissue thickening.

From the Department of Radiology, The Jikei University School of Medicine, Tokyo, Japan.

Address correspondence and reprint requests to Shinjiro Tojo, MD, Department of Radiology, The Jikei University School of Medicine, 3-25-8, Nishi-Shimbashi, Minato-ku, Tokyo, Japan 105-8461; E-mail:

Acknowledgment date: February 27, 2012. First revision date: June 28, 2012. Second revision date: August 23, 2012. Acceptance date: August 26, 2012.

The device(s)/drug(s) is/are FDA approved or approved by corresponding national agency for this indication.

No funds were received in support of this work.

No relevant financial activities outside the submitted work.

© 2013 Lippincott Williams & Wilkins, Inc.