Magnetic resonance imaging of upper cervical disorders in rheumatoid arthritis.

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 roentgenograms: 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 cervical spine.