MRI appearance of lumbosacral spine in a patient with ankylosing spondylitis and cauda equina syndrome

Cauda equina syndrome is an unusual complication of ankylosing spondylitis. We present a case of a 68-year-old woman with long-standing ankylosing spondylitis who developed cauda equina syndrome. MRI revealed a characteristic widening of the lumbosacral thecal sac and numerous dorsal thecal diverticula. MRI is a powerful, noninvasive tool to confirm the diagnosis and exclude a treatable compressive lesion and provides a good alternative to myelography, an invasive and potentially dangerous procedure in such patients.