What is the role of MRI in the workup of rheumatoid arthritis (RA) of the cervical spine?

Updated: Aug 13, 2019
  • Author: Steven R Garfin, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

Magnetic resonance imaging (MRI) has provided an increased ability to visualize the extent of spinal cord compression, particularly when due to pannus. [44] Dvorak and colleagues showed that two thirds of patients with atlantoaxial subluxation (AAS) have a pannus of greater than 3 mm in diameter. [45] Therefore, the bony canal diameter measured on plain radiographs may not represent the true space available for the cord. Kawaida et al demonstrated spinal cord compression in all patients with rheumatoid arthritis when the space available for the cord (as measured on MRI) was 13 mm or less. [46]

On MRI, the cervicomedullary angle is an effective indicator of cord distortion from superior migration of the odontoid (SMO). This angle incorporates lines drawn along the anterior aspects of the cervical cord and along the medulla. The normal range is 135-175°. Angles less than 135° indicate basilar invagination and have been associated with myelopathy (see the image below for a patient example).

Rheumatoid spondylitis. MRI of a patient with supe Rheumatoid spondylitis. MRI of a patient with superior migration of the odontoid and subaxial subluxation. Courtesy of Steven R. Garfin.

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