A patient with longstanding ankylosing spondylitis (AS) developed a cauda equina syndrome. The myelogram showed a block at the L2 level. Vertebral computerised tomography showed calcification in the centre of the spinal canal. The patient also had features suggestive of a diffuse idiopathic skeletal hyperostosis (DISH). Meningeal calcification has never been reported in AS, so we suggest that this is related to an associated DISH. Cauda equina syndrome has not been described in DISH, and calcification of meninges has not been reported in AS, so we suggest that the meningeal calcifications and associated cauda equina syndrome are related to DISH.