[Sacral intradural arachnoid cysts as the cause of lumbar syndrome].

In two female individuals (37 and 47 years old) sacral intradural arachnoid cysts caused low back pain and sciatica for several years until the correct diagnosis was established by MR imaging. Both patients had micturition disturbances (pollakisuria). In both cases a sacral laminectomy was carried out and the dorsal border of the cyst wall was resected (marsupialisation) after evacuation of xanthochrome fluid. Neither cysts showed any communication with the subarachnoid space. Postoperatively the patients were free of complaints; pollakisuria disappeared within 2-4 weeks.