[Postoperative lumbar extradural arachnoid cyst. Report of two cases and review of the literature].

Two cases of postoperative extradural arachnoid cyst in the lumbar region were reported. The symptoms such as lumbago, sciatica and paresis of foot which were perfectly cured at discharge relapsed after several months of daily business. The two patients were readmitted and reexamined by myelography and computer assisted tomography. In the two patients a cystic pooling of metrizamide having a connection with the subarachnoid space was noted in the same way. At the second operation a small dural tear and an extradural arachnoid cyst were recognized similarly. Burres and coworkers reported that an extradural arachnoid cyst would easily grow through a small dural defect in the lumbar region, because the hydrostatic pressure is higher than that of the cervical level. Our two cases might well coincident with their theory. In consequence of the experience of the two postoperative extradural arachnoid cyst, we give emphasis that even though the dural tear would be small, especially in the lumbar region, it should not be overlooked and be closed carefully with fine sutures.