Upper cervical spine was examined with magnetic resonance imaging (MRI) and conventional roentgenograms in 55 patients with rheumatoid arthritis. The MRI findings were compared with various values determined in roentgenogramscolon; the atlanto-dental interval (ADI), the space available for the spinal cord (SAC), and the Ranawat and Redlund-Johnell values. In patients with vertical settling (VS), MRI showed medullary compression in all those with abnormal Redlund-Johnell values and Ranawat values of 7 mm or less. In patients with anterior atlanto-axial subluxation, compression of the upper cervical cord was observed in all patients with SAC of 13 mm or less and many of those with ADI of 8 mm or greater. This study indicated that medullary compression can be estimated by these values determined in roentgenograms of the cervial spine.
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