Localization of asterion and its relationship to the transverse and sigmoid venous sinuses.

Background: Asterion has been recognized as the external skull landmark for localization of the transverse and sigmoid sinus junction (TSJ). This study aimed to localize the asterion using the intersection of the Frankfurt horizontal plane (FHP) line and a vertical line from the mastoid tip, and to determine its relationship with the transverse and sigmoid sinuses.

Materials and methods: Distances from the asterion to the FHP and vertical line were measured on 200 dry skulls (100 males and 100 females). In addition, 48 cadavers (24 males and 24 females) underwent asterion drilling, and the relationship with the transverse and sigmoid sinuses was recorded.

Results: In most skulls, the asterion was superior to the FHP line, with average distances of 0.5 ± 0.3 cm on both sides. Distances to the vertical line were 3.7 ± 0.4 cm and 3.9 ± 0.4 cm for the left and right sides, respectively. These distances were statistically significant different between sides but not between sexes. The location of asterion was mainly over the TSJ (54%) and transverse sinus (42%). The accuracy of a predictive method was evaluated in additional 10 cadavers. The predicted positions were located with distances ranging from 0 to 1.3 cm in the horizontal plane (0.4 ± 0.4 cm) and 0 to 0.7 cm in the vertical plane (0.3 ± 0.2 cm) from the asterion.

Conclusions: This study confirms the anatomical relationship between the asterion and TSJ including the transverse sinus. Alternative method for localizing the asterion was also introduced.