Magnetic resonance imaging of cauda equina syndrome in long-standing ankylosing spondylitis.

The cauda equina syndrome is an uncommon complication of long-standing ankylosing spondylitis and its aetiology is controversial. We report a case of the cauda equina syndrome, erosion of the posterior elements of the lumbar spine and traction of the lumbar nerve roots because of multiple dural diverticula in a patient with long-standing ankylosing spondylitis. Magnetic resonance imaging is valuable in excluding other spinal lesions. Extensive dural diverticula formation is characteristic of ankylosing spondylitis and has the potential to provide an early diagnosis.