A 37-year-old male presented with progressive lower extremity paraparesis of 3 years duration (motor power of 3/5 in both legs with a 0/5 left foot drop for 1 year). There were no history of back pain, significant trauma, spinal surgery/lumbar puncture, or tuberculosis.
The thoracic MR showed, on axial cuts, an arachnoid cyst with lateral extension into both neural foramina between the T12-L1 levels; no further lesions were noted on the cervical or lumbar MR studies.
The patient underwent L1 preserving laminectomies from T11 to L2 [Figures 1-3], revealing a distended cyst. Thinning of the dura with arachnoid herniation was observed involving both T12-L1 neural foramina (e.g., especially on the right). The dural defect was directly repaired using a nonabsorbable monofilament suture made of expanded polytetrafluoroethylene (GORE-TEX) plus application of a small muscle patch graft. The wound was then routinely repaired in layers, with a drain placed in the epidural space.
The histopathological examination revealed collagenous tissue within the wall of the cyst with occasional cuboidal and flattened cells, suggestive of a meningothelial reaction.
Immediately after surgery, the patient had dramatic relief in his symptoms. The follow-up MRI 3 months later confirmed complete excision of cyst and thecal sac decompression. By 9 postoperative months, the patient was completely asymptomatic.