Large Thoracolumbar Extradural Arachnoid Cyst Excised by Minimal Skipped Hemilaminectomy: A Case Report
A 43-year-old man presented with back pain and radiating pain of both legs for 5 years. The symptoms had developed over last 1 year. Neurologic examination revealed mild voiding difficulty. There was no history of trauma, lumbar puncture, any surgery and spinal infection. Plain radiography and computed tomography (CT) of thoracolumbar spine revealed thinned pedicles, increased diameter of spinal canal, and posterior scalloping of the vertebral bodies at T10 to L1. Magnetic resonance imaging (MRI) demonstrated a large extradural cystic lesion at T10-L1 levels with extension into the foramen and extra-foramen. The cystic lesion was iso-intense compared with CSF on T1 and T2-weighted images and no enhancement after gadolinium administration was showed (). The preoperative diagnosis was spinal extradural arachnoid cyst. Because the closure of dural defect is important for prevention of recurrence, the preoperative radiologic studies were performed to detect the dural defect. First, cine-MRI and magnetic resonance (MR) myelography were performed. We were not able to confirm the communication site by cine-MRI and MR myelography. Additionally, CT myelography was performed. It showed contrast medium leakage at T12 vertebral body lower margin (). This finding provided an evidence of a communication between the extradural cyst and normal subarachnoid space. We could localize the communication site between the cyst and subarachnoid space before the operation.\nFirst of all, right hemilaminectomy was performed from low part of T11-upper part of L1 for exploration of the communication site. A huge epidural arachnoid cyst was exposed and outer wall was incised. The yellowish cyst fluid was expelled. The cystic mass was easily separated from the dorsal thecal sac. Then, additional hemilaminectmy was performed at T10 and upper portion of T11, leaving two third of T11 lamina. The upper margin of the cyst was exposed and separated from the dura sac. Without partial resection, the separated upper part of the cyst was passed beneath L1 lamina and continually separated. But, cystic wall extending to right foramen of T11/12 was not separated due to adhesion with surrounding tissue. So, the cyst was excised, leaving small remnant at right foramen of T11/12. After removing the cyst, we found a small dural defect and CSF leak at the dorsal thecal sac at T12/L1. After repairing the defect with primary suture, the site was sealed using fibrin glue. There were no post-operative complications. The patient's pain improved rapidly. After 10 days, the patient was discharged. At 1 year after the operation follow up, CT and MRI demonstrated no recurrence (). Dynamic plain X-ray revealed no instability and kyphotic deformity.