Introduction: We report a rare case of idiopathic spinal herniation (ISCH) with an unusual course.

Case Presentation: A 56-year-old male presented with urinary incontinence and weakness in the left lower limb. Magnetic MRI of the thoracic spine suggested ventral displacement of the spinal cord at the T2 vertebral level, raising the suspicion of an extradural escape of the spinal cord. The patient was diagnosed with ISCH at the T2 level and was scheduled for surgery. During the procedure, we observed a direct extradural escape of the spinal cord ventrally. Following the reduction of the herniated tissue, we also directly sutured the herniation defect. Postoperatively, the patient's symptoms improved and his condition stabilised. However, 4 years and 2 months later, the patient returned with complaints of gait disturbance and decreased strength in the left lower limb. Magnetic resonance imaging (MRI) revealed ventral displacement of the spinal cord at the T2 level, indicating recurrence of the spinal herniation. Surgical revision was decided. Upon incision of the dorsal dura, we found a cystic mass extending cephalad and caudad. The site of the previous suturing did not show any herniation recurrence. However, new evidence of spinal cord entrapment was identified caudally. After reducing the entrapped spinal cord, the outer layer of the dura mater was observed through a defect in the inner layer. We directly sutured the herniation defect in the inner layer and reinforced it with a covering material before surgical closure.

Conclusion: This case report illustrates the consequence of continuous dorsal pressure on the spinal cord from a cystic mass that developed postoperatively, resulting in a defect in the intrinsically vulnerable ventral dura mater and the formation of a new spinal herniation.