Symptomatic Thoracic Nerve Root Herniation into an Extradural Arachnoid Cyst: Case Report and Review of the Literature.

Background: Spinal extradural arachnoid cysts (SEACs) are relatively rare and usually asymptomatic. They preferentially are situated in the thoracic extradural space and almost always dorsal. SEACs may present with back pain and/or cord compression symptoms.