Circumferential venous sinus: an innovative separation method for total vertical type II craniopagus twins.

Craniopagus twins, particularly the total vertical type II variant, represent one of the rarest and most complex congenital malformations, with significant surgical challenges. This technical note presents the successful staged separation of craniopagus twins at 3 years 9 months of age, the oldest known to be separated to date. The twins shared a prominent circumferential venous sinus, requiring a novel surgical strategy. Advanced imaging, 3D modeling, and virtual reality planning in the metaverse-between Brazil and the United Kingdom-guided the 7 staged surgeries. Initially, partial separations focused on the more vulnerable twin. However, arteriographic evidence of venous dependency led to a paradigm shift, in which the authors performed the final stages on the other twin to preserve critical venous outflow. This innovative approach allowed division of the shared venous sinus without neurological compromise. The final separation, completed in 2 stages over 31 hours, resulted in successful independent circulations and recovery. This case highlights the importance of individualized surgical planning, collaborative international simulation, and the potential for adapting separation protocols based on venous architecture.