Case Report: Spinal cord herniation associated with ankylosing spondylitis

Spinal cord herniation (SCH) is a rare clinical entity characterized by the ventral displacement of the spinal cord through a dural defect. While often classified as idiopathic, SCH associated with ankylosing spondylitis (AS) is exceedingly rare. The pathogenesis in such cases remains unclear, and treatment strategies are not well standardized.

Herein, we report a series of four patients with long-standing ankylosing spondylitis who presented with SCH between August 2018 and August 2021. All patients exhibited severe thoracolumbar kyphosis and restricted spinal mobility. Uniquely, the herniations occurred at the vertebral body level rather than the disc level, and one patient presented with rare multilevel herniations. Two patients underwent pedicle subtraction osteotomy (PSO) with spinal fusion. In both surgical cases, direct dural repair was avoided; stabilization was achieved through indirect cord relaxation via spinal column shortening. Postoperative imaging showed successful kyphosis correction and stabilization of the herniation.

SCH in patients with AS is a distinct entity secondary to inflammatory and biomechanical changes. PSO with fusion is a viable surgical option that addresses both deformity and cord tethering through an indirect mechanism.