Localization of key holes in adult retrosigmoid sinus approach based on skull surface anatomic markers

Abstract

Objective To explore the application value of skull surface markers which are easy to be exposed in the operation of retrosigmoid sinus approach to establish coordinate system in the location of key holes. Methods The thin slice CT of 80 patients with trigeminal neuralgia or hemifacial spasm from the image database of Linyi Central Hospital of Shandong Province from January 2019 to January 2020 were selected for three⁃dimensional (3D) imaging. The coordinate system was constructed by the vertex of digastric sulci (point A), the intersection of temporal scale and parietal lacustrine suture (point B) and star point (point C). A total of 60 patients who were hospitalized in our hospital from May 2020 to May 2022 and required retrosigmoid sinus approach for microvascular decompression (MVD) were selected and randomly divided into reconstruction group, non⁃reconstruction group and control group, with 20 cases in each group. In reconstruction group, after the construction of the coordinate system during the surgery, the center of key hole in 3D skull model constructed before surgery was used to locate the location. In non⁃reconstructed group, after the intraoperative construction of coordinate system, the key hole positioning law of the imaging model was used as the center of the key hole. In control group, no coordinate system was established during the operation, and the center of the key hole was taken as the star point. After the center of the key hole was determined, MVD was performed routinely in all groups. The 3D skull model was constructed after surgery, and bone window area, bone defect area, the actual center of key hole (R0) and the center of ideal key hole (R, D value) were measured. Results The results of the imaging model showed the average coordinates of point R were [(4.60±3.89) mm, (4.88±4.14) mm], and the approximate coordinates were (5 mm, 5 mm) after the establishment of the coordinate system with the vertex of digastric sulcus (point A), the intersection of temporal scale and parietal lacustrine suture (point B) and star point (point C). The coincidence rate between the intersection of temporal scale and parietal lacustrine suture and the transverse sinus groove was 95.63% (153/160), and the coincidence rate between the intersection of temporal scale and parietal lacustrine suture and the vertex of digastric sulcus and the superior curve of sigmoid sinus groove was 93.13% (149/160). The coincidence rate between the intersection of temporal scale and parietal lacustrine suture and the vertex line of digastric sulcus and the superior and vertical segment of sigmoid sulcus was 71.25% (114/160). The results showed the bone window area, bone defect area and D value were significantly different among 3 groups (P=0.000, for all), and the bone window area, bone defect area and D value in reconstruction group and non⁃reconstruction group were all smaller than those in control group (P＜0.01, for all). Bone window area (P=0.009) and D value (P=0.000) in reconstructed group were also smaller than those in non⁃reconstructed group. Conclusions In the absence of preoperative CT 3D reconstruction of the skull, a coordinate system was established with the vertex of the digastric sulcus (point A), the intersection of temporal scale and parietal lacustrine suture (point B) and star point (point C), and a bone window was formed with the coordinate point (5 mm, 5 mm) as the center of the key hole to better locate the location of the key hole.

Keywords

• skull
• anatomic landmarks
• microvascular decompression surgery
• computers
• analog
• neuroanatomy