Introduction

Ankylosing spondylitis is the most common of the spondyloarthritides—the group of chronic inflammatory diseases of the axial skeleton that result in low back pain, spinal stiffness and restriction of movement. Extra-axial complications include peripheral arthritis, enthesitis (inflammation of the insertion of tendon into bone) and uveitis. In ankylosing spondylitis, chronic inflammation leads to ossification of the outer fibres of the annulus fibrosus of the intervertebral discs. The curved, bony spicules bridging the vertebral bodies give the impression of a bamboo stem on antero-posterior X-rays of the spine. Neurological complications are uncommon in ankylosing spondylitis and comprise mainly traumatic spinal cord injury (table 1).1 We report a rarely encountered slowly progressive neurological complication: the ‘cauda equina syndrome in ankylosing spondylitis’.1 ,2