Combination of transverse myelitis and arachnoiditis in cauda equina syndrome of long-standing ankylosing spondylitis: MRI features and its role in clinical management.

The cauda equina syndrome (CES) is a rare neurological complication of ankylosing spondylitis (AS). Imaging diagnosis of CES in long-standing AS patients (CES-AS) using myelography, computed tomography (CT), and magnetic resonance imaging (MRI) were reported in the literature. They, however, demonstrate only the chronic abnormalities of CES-AS, i.e., dural ectasia, dorsal dural diverticula, and selective bone erosion at the posterior elements of the vertebrae. To our knowledge, imaging features of acute intradural inflammation in CES-AS were not described. We report a patient of CES-AS in whom MRI disclosed acute transverse myelitis and arachnoiditis along the lower spinal cord, and discuss the pathogenesis of CES-AS and the role of MRI in clinical management.