Intrasacral extradural arachnoid cysts.

Three patients presented with rare intrasacral extradural arachnoid cysts manifesting as sensory deficiencies and pain in the lower extremities. Magnetic resonance imaging with various sequences identified the cysts. Two patients underwent surgery via laminectomy of the sacrum for cyst exploration and disconnection of the cyst with the dural theca. Postoperative outcome was favorable in these two patients. Intrasacral extradural arachnoid cyst should be considered in the differential diagnosis of low back pain.