Interdural Spinal Cyst: A Rare Clinical Entity.

Background For more than 2 decades, dural spinal cysts have been broadly classified as extradural and intradural. Case Description A 40-year-old woman presented with radicular thoracic pain. Intraoperative findings showed the cyst to be present within the dura itself. Conclusions We suggest a revised classification of spinal dural cysts. This case highlights that, during surgery for spinal meningeal cysts, surgeons should bear in mind the possibility of an interdural cyst. This may help avoid inadvertent tears in the deep layers of such cysts, thus maintaining dural patency.