Surgical management of a thoracic extradural arachnoid cyst with communication to subarachnoid space through nerve root: a case report.

Spinal extradural cysts are uncommon and may cause cord and nerve root compression. The cysts usually appear in thoracic spine. We report a 29-year-old man with an extradural arachnoid cyst from T4 to T6. The cyst was communicated to the subarachnoid space through a fistula at the left T6 nerve root. To access the fistula, we had to unroof the foramen of left T6 nerve root which could lead to spinal instability. We decided to save the bony and soft tissue elements of the foramen at the mentioned thoracic spine level. Therefore, the cyst walls were excised and then the ostia of the cyst at the cystic side of the fistula was tightly closed.