Surface Landmarks Combined With Image-guided Sinus Location in the Retrosigmoid Approach and Their Clinical Feature Analysis

Abstract Background During craniotomy for the cerebellopontine angle (CPA) lesion by the typical retrosigmoid approach, the exact exposure of the margin of the venous sinuses complex remains an essential but risky step. This study aimed to reveal the exact position of asterion and sinuses by combining preoperative imaging with intraoperative landmarks. and analyse their clinical features. Methods From February 2008 through November 2019, 94 patients who underwent removal of vestibular schwannoma (VS) through retrosigmoid craniotomies were enrolled in the series. We utilized preoperative images, including computed tomography (CT) and/or magnetic resonance imaging (MRI) combined with intraoperative anatomical landmarks, to determine the exact location of the sigmoid sinus and the transverse and sigmoid sinuses junction (TSSJ). MRI T1 sequences with gadolinium and/or the CT bone window were used to measure the distance relationship of the asterion to the sigmoid sinus.Results In 94 cases of retrosigmoid craniotomies, we observed the asterion lay 12.71 millimeter on the posterior to the body surface projection of the TSSJ averagely. Intraoperative surface landmarks combined with preoperative image information identifying the distance from the asterion to sigmoid sinus at the transverse sinus level, enabled an appropriate initial burr-hole (the margin of the TSSJ ). Just one case had a minor laceration of the sigmoid sinus when the bone flap was opened.Conclusions By combining intraoperative anatomical landmarks with preoperative image information, the margin of the venous sinuses, especially the inferior margin of the transverse sinus in the retrosigmoid approach can be well and truly identified. The distance from the intersection of the asterion and occipitomastoid suture to the TSSJ is the shortest between the occipitomastoid suture and the sigmoid sinus.