Intraoperative demonstration of a check-valve mechanism in a spinal extradural arachnoid cyst with nerve root incarceration

Achoimre

Abstract Spinal extradural arachnoid cysts (SEDACs) are rare lesions thought to arise from a dural defect associated with a check-valve mechanism, although direct intraoperative evidence is limited. We report a 17-year-old female presenting with persistent low back pain and bilateral lower extremity numbness. Magnetic resonance imaging demonstrated a cystic lesion at the Th12–L1 level displacing the dural sac, while computed tomography myelography failed to identify a communicating tract. Surgical exploration was performed due to persistent symptoms and a suspected dynamic mechanism. Intraoperatively, a dural defect at the nerve root sleeve with nerve root incarceration was identified. Cerebrospinal fluid leakage ceased after closure of the defect, confirming a check-valve mechanism. The cyst was resected and the defect repaired. The patient’s symptoms resolved completely, with no recurrence at 2-year follow-up. This case provides direct intraoperative evidence of the proposed pathophysiology of SEDAC.