Unexpected Intradural Lumbar Disk Herniation Found During Transforaminal Endoscopic Surgery

Background: Intradural disk herniation (IDH) is defined as the displacement of the intervertebral disk nucleus pulposus into the dural sac. In this lumbar lesion, the affected level differs from that of a traditional extradural herniation: 55% of cases occur at the level of L4-5, 16% at L3-4, and 10% at L5-S1. Upper lumbar IDH is extremely rare. We present a case of an IDH at the level of L2-3 that was diagnosed during endoscopic surgery.

Case description: A 65-year-old male patient presented with severe radiating pain in the anterior right thigh that was accompanied by a tingling sensation in the right calf and difficulty in walking. Physical examination showed normal strength. Bladder and bowel function was normal, but mild hypesthesia of the L3 sensory dermatome was observed. Magnetic resonance imaging revealed a herniated disk at the level of L2-L3 that was compressing the right side of the dura. A percutaneous transforaminal endoscopic lumbar diskectomy was planned. After foraminoplasty, no ruptured disk fragments could be found. During dissection of the adhesion between the dura and protruded disk, the dura was torn. Interestingly, through this dural opening, multiple fragmented disk portions were visualized among the nerve rootlets. We removed some of the soft disk material; however, complete removal of the disk fragments was predicted to damage the rootlets, and we decided to convert to microscopic surgery. The disk fragments were successfully removed via durotomy under microscopic assistance. The incised dorsal dura was primarily sutured with continuous stitches, and the defect on the ventrolateral side of the dura was patched and sealed using a harvested inner ligamentum flavum and Gelfoam (Pfizer, New York, New York, USA). After the operation, the patient's symptoms improved. There was no cerebrospinal fluid leakage.

Conclusions: If there is any preoperative clinical or radiologic suspicion of IDH, a microscopic surgical approach should be considered to be the first-line option, as this is a safe and effective method for achieving IDH removal and dura repair without a postoperative neurologic deficit. Even during endoscopic surgery, if the surgeon expects even minor complications, we suggest converting to open surgery. In addition, the adequate sealing of the dura may be sufficient to prevent cerebrospinal fluid leakage, without the need for dural suture and lumbar drainage.