[Cauda equina syndrome in ankylosing spondylitis].

A 55-year-old man who has had ankylosing spondylitis for over 20 years developed gradually increasing pain and sensory disorders in the legs, as well as mild foot and toe elevator weakness. There was no evidence of inflammatory activity. Clinical, neurophysiological and neuroradiological examination revealed a cauda equina syndrome as a late complication of ankylosing spondylitis. There is no known causal treatment.