Traumatic Lumbar Interdural Cyst with Intradural Expansion and Compression of the Cauda Equina: Case Report and Surgical Video.

Intradural arachnoid cysts are common entities that can be congenital, or caused by infectious, inflammatory, or even traumatic processes. However, true "inter"-dural cysts formed between the two lamellae of the lumbar dura without any fistulous arachnoid connection are rare. We present the case of a post-traumatic interdural cyst formation of the lumbar spine that compressed the roots of the cauda equina causing acute unrelenting pain. The cyst walls were formed by the true dural layers, and the cavity was filled with blood degradation products without any arachnoid connection to the subdural space. A commented video that details the diagnostic and surgical aspects of this case, alongside intraoperative footage is provided.