The cuneus vein: initial anatomical description and preservation technique for posterior interhemispheric approaches

Abstract Background and objective The posterior interhemispheric approach provides optimal access to lesions located in a number of areas. A major advantage of this approach is that the parieto-occipital vein is typically the only venous structure encountered, which minimizes venous interference during exposure. In a surgical series of 12 patients, we identified a previously undescribed venous variant extending from the cuneus to the falx cerebri. Here, we characterize this venous structure and propose a microsurgical strategy to preserve it. Methods A total of 303 posterior interhemispheric approaches were performed from September 2005 to August 2025. We retrospectively reviewed clinical and radiological data collected from patients’ electronic medical records and searched the operative database to locate surgical videos. Results In 12 patients undergoing the posterior interhemispheric approach (12/303, 4%), we identified a previously unreported venous variation in which a cortical vein extended from the cuneus to the falx cerebri. We have termed this structure the cuneus vein . Among these 12, 2 were observed during a right-sided approach (2/157, 1.3%) and 10 during a left-sided approach (10/146, 6.8%). The vein-releasing technique was used in 7 patients, while the falx-cutting technique was done in 4. In all but one patient, the cuneus vein was successfully preserved. In one patient with hydrocephalus, excessive brain relaxation after CSF drainage limited mobilization and caused vein injury, without hemorrhagic or ischemic morbidity during follow-up. Conclusions The cuneus vein, a cortical vein extending from the cuneus to the falx cerebri, is an anatomical variation that has not been described previously but requires careful consideration during the posterior interhemispheric approach. The cuneus vein drains the visual cortex; thus, its sacrifice may lead to postoperative complications, including visual deficits secondary to venous infarction. In this study, we identified and characterized this venous variation and demonstrated its preservation using the vein-releasing technique and the falx-cutting technique.