Gas-filled intradural cysts of the lumbar spine and the possible pathogenesis.

Background Context: There have only been four reports of gas-filled intradural cysts, and the pathogenesis is unknown.

Purpose: To document the radiologic and histopathologic features of gas-filled intradural cysts and to discuss the pathogenesis with a review of the literature.

Study Design: Case report.

Methods: A 67-year-old woman, admitted to our institute, presented with severe right thigh pain. On admission to the institute, enhanced magnetic resonance imaging, showed a cystic lesion in the spinal canal at the L2-L3 level, with an intensity suggesting the presence of gas. An enhanced region around the cyst was noted. Computed tomography after discography also revealed a water-soluble contrast filled the subarachnoid space and area around the cyst, but not inside.

Results: The cyst was surgically resected. One of the nerve roots was firmly adherent to the gas-filled cyst. The cyst wall comprised fibrous tissue, including small granulations and herniated disc material.

Conclusion: Gas-filled intradural cysts are rare. The pathogenesis appears to involve gas in a degenerated intervertebral disc, and spontaneous absorption of herniated disc material.