Rethinking the sphenoparietal sinus: implications for lesser sphenoid wing dural arteriovenous fistulas. Illustrative cases.

backgroundDural arteriovenous fistulas (dAVFs) of the lesser sphenoid wing (LSW) are exceedingly rare, and their angioarchitectural features, natural history, and optimal management remain poorly defined. OBSERVATIONS: The complex anatomy of the sphenoparietal sinus and its controversial relationship with LSW-dAVFs necessitate precise, LSW-specific terminology to guide management. Starting from these premises, 3 patients with LSW-dAVF (Borden type III) underwent microsurgical treatment. Across the authors' series and 19 papers from the literature, LSW-dAVF showed arterial supply from the middle meningeal artery (89.3%) and the ophthalmic artery (OphtA) (60.7%). Venous drainage typically occurred through a bridging vein originating from the LSW, immediately lateral to the superior orbital fissure, with secondary recruitment of the superficial and deep sylvian veins. An endovascular approach was selected as the first-line treatment in 64% of 28 reported cases, and complete angiographic occlusion was achieved in about one-third of these procedures (endovascular failure rate approximately 67%). In contrast, microsurgical clip ligation resulted in complete obliteration in all surgically treated patients, with no reported mortality. LESSONS: The complex angioarchitecture of LSW-dAVFs favors microsurgical management, as it provides direct access, definitive cure, and low morbidity. Endovascular therapy is limited by the anatomical features of these fistulas, which predispose to incomplete occlusion with the risks associated with navigation of the OphtA. https://thejns.org/doi/10.3171/CASE26129.