Sacral meningeal cyst associated with valve-like mechanism--case report.

A 58-year-old woman presented with low back pain radiating to the lower extremities. Magnetic resonance imaging revealed a cystic lesion in the sacrum compressing the nerve roots. At operation, a valve-like communication was found between the subarachnoid space and the cyst cavity in the vicinity of the sacral nerve root. The communication was obliterated with a purse-string suture and reinforced with a free muscle graft. Postoperatively, she reported improvement of the pain. Valve-like communication between the cyst cavity and subarachnoid space can cause enlargement of spinal meningeal cyst, and could also explain enlargement of sacral meningeal cyst. Surgical obliteration of the communication rather than the cyst resection is more important for sacral meningeal cyst.