Giant sacral meningeal diverticula: surgical implications of the "thecal tip" sign. Report of two cases.

Abstract

The surgical anatomy of giant sacral meningeal diverticula varies greatly depending on whether they develop ventral or dorsal to the thecal sac and spinal nerve roots. The ability to distinguish between the two lesion types preoperatively is therefore advantageous. The authors present a method of distinguishing ventral from dorsal meningeal diverticula on magnetic resonance imaging using the "thecal tip sign." They also describe the differences in operative technique required for resection of each type of diverticular cyst.