[Association of ankylosing spondylarthritis, cauda equina syndrome and dilatation of the lumbar cul-de-sac with voluminous arachnoid diverticulum. Clinical, radiological and tomodensitometric study of a case].

The authors report a clinical and radiological observation of cauda equina syndrome associated with ankylosing spondylitis. Although only 32 cases have been reported in the literature over the last twenty years, such an association is probably not exceptional. The mode of onset and the course of the neurological symptoms is quite similar from case to case: ankylosing spondylitis preexisting for many years, and inactive when neurological signs develop, the latter usually being very slowly progressive. The usual radiological features, demonstrated by saccoradiculography in the supine position, are posterior diverticulas of the lumbar theca, contiguous to bony erosions of the laminae, well visualized by computed tomography. Pathogenesis remains obscure, and none of the attempted therapies, including surgical procedures, have proved effective.