Arachnoid cysts most probably arise from incomplete separationof the perimedullary mesh (endomeninx) during the early stages ofembryogenesis.Arachnoid cysts present due to compressing adjacent neuralstructures, increasing the intracranial pressure by their own mass effectand by obstructing CSF flow and causing hydrocephalus.Endoscopic management of arachnoid cysts is a safe and effectivemodality provided that each case is approached individually and studiedcarefully intraoperatively.