Cauda equina syndrome due to dural sac shift with engorgement of the epidural venous plexus. Rare complication after lumbar microdiscectomy

Abstract Background Several postoperative complications related to lumbar microdisectomy have been reported, including cauda equina syndrome. However, to the best of our knowledge, postoperative cauda equina syndrome resulting from dural sac shift with engorgement of the epidural venous plexus is yet to be reported. Case description A 71-year-old male patient was referred to our hospital with a chief complaint of pain and sensory disturbance due to the lumbar disc herniation of L5-S1. Microdisectomy was performed to treat the lumbar disc herniation, and his sensory disturbance improved. However, from postoperative day 2, he started to complain of motor weakness, sensory disturbance of S2 and difficulty in urination. Magnetic resonance image showed the dural sac shifted to the bone window of L5-S1 with engorgement of the ventral epidural venous plexus. The dural sac shift was thought to be the cause of postoperative cauda equina syndrome, and laminoplasty was chosen to return the dural sac shift into the spinal canal. Cauda equina syndrome completely resolved after laminoplasty. Postoperative magnetic resonance image showed the reduction of the dural sac into the spinal canal. The patient was discharged from the hospital without any residual clinical symptoms. Conclusion We report a rare case of postoperative cauda equina syndrome due to dural sac shift, and discuss the nascent mechanism of the dural sac shift focusing on anatomical features of the dural sac. We also propose laminoplasty as an option to treat dural sac shift with engorgement of the epidural venous plexus.