Fig. 3

CT-VR reconstruction reveals an enlarged mastoid foramen (2.5 mm in diameter) (A). Keyhole positioning is flush with the zygomatic arch’s inferior margin, orthogonal to the line extending from the digastric groove’s point (1 cm distally). Simulated extent of bone window removal illustrated by the blue coil (B). Simulations depict a transverse incision at the transverse sinus’s base and a retroauricular oblique incision, with the former selected (C). Unobstructed visualization of CN-V, neighboring SPVC, and positions of PICA, VA, and SCA in the simulation (D). Intraoperative examination confirms spatial relationship between CN-V, REZ, SPV, PICA, and VA, corroborating preoperative simulations (E). Teflon felt strategically placed intraoperatively to segregate CN-V from PICA and VA (F)