Congenital/primary clival meningocele: A systematic review and surgical approach based on a new proposed classification.

Skull base meningoceles are extremely rare, most commonly resulting from congenital defects in sphenoid bone fusion. Inadequate embryonic fusion between the posterior sphenoid and the occipital bones may result in a transclival meningocele. Given the absence of a formal classification system for clival meningoceles and clear guidelines for the most appropriate endoscopic skull base surgical approach, we combined an anatomical study and a systematic review to characterize anatomical patterns, propose a preliminary classification, and discuss transoral and endonasal surgical corridors according to each clival subtype. In addition, we report the first known case of a primary clival meningocele successfully treated via a transoral endoscopic approach. The study was registered with PROSPERO (CRD42024575282) and received approval from the Ethics Committee (82878724.1.0000.5259). The systematic review followed PRISMA guidelines. PubMed/MEDLINE, Embase, and Cochrane were rigorously searched. Anatomical dissection of midsagittal skull base specimens was performed to assess surgical access to clival regions. Seventeen studies comprising 18 patients (mean age 30.7 years; 72.2% female) were included. Clival defects were classified as posterior transsphenoidal (n = 11), spheno-occipital (n = 1), and basioccipital (n = 6). The endoscopic endonasal approach appeared more appropriate for posterior transsphenoidal cases and the transoral route for basioccipital defects. Anatomical dissection studies confirmed that the endonasal corridor is more suitable for the upper third of the clivus and the transoral route for the lower third.