A 3D-Computed Tomography Angiography Study to Help in Surgical Planning for Retrosigmoid Craniotomies

Aims and Objectives: It is impossible to precisely anticipate the course of the transverse and sigmoid sinuses and theirindividual relationship to superficial landmarks such as the asterion during retrosigmoid approaches. This study was done todetermine the position of the asterion and the relationship between asterion and the transverse-sigmoid sinus junction (TSSJ)in making precise burr hole without damaging sinuses during retrosigmoid craniotomies.Materials and Methods: Computed tomography (CT) angiography was performed in 50 patients to obtain 3D-CT volumerendering images of cranial bone and dural sinuses. After delineating the sinuses, by simple restructuring using software andopacity modulation, bone image is reinforced. Asterion type, distance from the tip of mastoid process to asterion and root ofzygoma (ROZ) to asterion, and location of asterion in relation to TSSJ and distance between asterion and TSSJ were analyzedand measured.Results: The incidence of type 1 (presence of sutural bones) in our study was 24% and type 2 (absence of sutural bones) was76%. There was no statistically significance in the side and gender differences. The distance between the asterion and fromthe ROZ was 54.70 ± 3.68 on the right side and 54.32 ± 3.41 on the left side (P-0.612). The distance between asterion and tipof mastoid was 50.51 ± 2.67 on the right side and 50.12 ± 3.06 on the left side (P-0.716). The asterion was located on the T-Ssinus complex in 36 (72%) cases. The asterion was below the T-S sinus complex in 13 (26%) cases, and above the T-S sinuscomplex in only 1 (2%) cases.Conclusion: 3D-CT volume rendering imaging is capable of accurately visualizing the bony landmark and dural sinuses. Aneasy and simple restructured image provides precision and safety for the patient by ready and easy localization of asterionand TSSJ. This study was done to show that the previous cadaver-based anatomical studies can be done now in a moresophisticated and accurate manner with the latest technological advancements. This offers new options for anatomic researchand morphometric investigations.