MRI DEMONSTRATION OF ARACHNOIDITIS IN CAUDA-EQUINA SYNDROME OF ANKYLOSING-SPONDYLITIS

The cauda equina syndrome is a rare but well-recognised complication o f longstanding anky-losing spondylitis, usually presenting when the jo int disease is quiescent. The clinical and radiological findings in a patient with only a 3-year history, in whom the onset of joint and neu rological symptoms was apparently simultaneous, are presented. MRI rev ealed characteristic expansion of the lumbar spinal canal with scallop ing of the pedicles, laminae and spinous processes, related to numerou s posterior dural diverticula. The quantity and extent of such diverti cula are unusual. We demonstrated adherence of individual nerve roots to the arachnoid surface of these diverticula and to each other. In a second patient, with a much longer history of both ankylosing spondyli tis and cauda equina syndrome, MRI again showed florid, multilocular d ural ectasia, marked irregularity and thickening of nerves, and adhere nce to the dural diverticula. These cases provide evidence for the rol e of arachnoiditis in the pathogenesis of the cauda equina syndrome of anky-losing spondylitis.