Mastoid notch as a landmark for localization of the transverse-sigmoid sinus junction

Abstract

Background: The top of the mastoid notch (TMN) is close to the transverse-sigmoid sinus junction. The spatial position relationship between the TMN and the key points (the anterosuperior and inferomedial points of the transverse-sigmoid sinus junction, ASTS and IMTS) can be used as a novel method to precisely locate the sinus junction during lateral skull base craniotomy.Methods: Forty-three dried adult skull samples (21 from males and 22 from females) were included in the study. A rectangular coordinate system on the lateral surface of the skull was defined to assist the analysis. According to sex and skull side, the data were divided into 4 groups: male&left, male&right, female&left and female&right. The distances from the ASTS and IMTS to the TMN were evaluated on the X-axis and Y-axis, symbolized as ASTS&TMN_ x, ASTS&TMN_y, IMTS&TMN_x and IMTS&TMN_y.Results: Among the four groups, there was no significant difference in ASTS&TMN_x (p = 0.05) and ASTS&TMN_y (p = 0.3059), but there were significant differences in IMTS&TMN_x (p < 0.001) and IMTS&TMN_y (p = 0.01), and multiple comparisons indicated that there were significant differences between male&left and female&left both in IMTS&TMN_x (p = 0.0006) and in IMTS&TMN_y (p = 0.0081). In general, the ASTS was located 1.92 mm anterior to the TMN on the X-axis and 27.01 mm superior to the TMN on the Y-axis. For the male skulls, the IMTS was located 3.60 mm posterior to the TMN on the X-axis and 14.40 mm superior to the TMN on the Y-axis; for the female skulls, the IMTS was located 7.84 mm posterior to the TMN on the X-axis and 19.70 mm superior to the TMN on the Y-axis. Conclusions:The TMN is a useful landmark for accurately locating the ASTS and IMTS.

The auricula as a new surgical landmark for the transverse-sigmoid-sinus-transition

“…Posterolateral skull base approaches around the SS are frequently used for middle and posterior fossa pathologies, such as the retrosigmoid approach for lesions in the cerebellopontine angle ( Hoz et al, 2022 ; Raso et al, 2011 ). Accurately localizing the anterosuperior and inferomedial points of the TSST, as well as the course of the SS, on the external surface of the cranium is important in lateral skull base craniotomies ( Li et al, 2020 ; Day et al, 1996 ). An abberant course of the SS forms a risk factor for unexpected bleeding during surgery ( Tsutsumi et al, 2020 ).…”

Phenotypical variability of the sigmoid sinus in translabyrinthine and retrosigmoid surgeries

“…To predict the localization of the sigmoid sinus in potential patients, authors advise using the external landmarks of the skull such as asterion, temporoparietal suture, and mastoid process [2,12]. Li et al (2020) designed the entire coordinate system using the mastoid notch as an essential reference point [6]. Practical application of this method would require speci c orientation of the patient's head and extensive skull exposure during the procedure.…”

Phenotypical variability of the sigmoid sinus in translabyrinthine and retrosigmoid surgeries

“…To predict the localization of the sigmoid sinus in potential patients, authors advise using the external landmarks of the skull, such as asterion, temporoparietal suture, and mastoid process [ 2 , 12 ]. Li et al designed the entire coordinate system using the mastoid notch as an essential reference point [ 6 ]. Practical application of this method would require specific orientation of the patient’s head and extensive skull exposure during the procedure.…”

“…The statistical differences for the distances between the various parts of the sigmoid sinus and posterior semicircular canal, facial nerve, internal and external acoustic meatuses for males and females, and the right and left sides of the head are available in the literature [ 2 , 12 , 14 ]. Several bony landmarks and laborious coordinate systems aimed to assist in localizing the sinus along were proposed by authors [ 3 , 6 ]. However, the influence of the shape of the skull on the position of the sigmoid sinus has never been reported.…”