Cauda Equina Syndrome in Ankylosing Spondylitis: Challenges in Diagnosis, Management, and Pathogenesis

Objective. Cauda equina syndrome (CES) is a rare neurologic complication of longstanding ankylosing spondylitis (AS). It is unclear what causes CES, and no proven or effective therapy has been reported to date. We have encountered 6 patients with longstanding AS diagnosed with CES. We set about to study their features, review the literature, and generate hypotheses regarding pathophysiology, as well as to speculate on the possibilities of early recognition and prevention. Methods. We obtained permission from 6 patients with longstanding AS and CES to access their medical records and imaging studies for research purposes related to this paper. We collected and reviewed each patient’s medical history, imaging studies, disease duration, past therapies especially those that relate to AS, laboratory data, as well as any treatment they received for CES and followup results of each case to the present time. Results. The 6 cases of CES with AS have remarkable similarity to each other in that several decades of the disease had passed before neurologic symptoms and later signs appeared. All cases have fused spines and facet joints without spinal fractures, spinal stenosis, or disc herniation. Conclusion. CES is a rare yet debilitating neurologic complication of longstanding AS. The pathophysiology and treatments are far from clear. We postulate that chronic enthesitis of the vertebral column initiates the process that results in dural stiffening and formation of ectasias, causing downstream nerve root damage.