Relationship Between the Superior Nuchal Line and the Lower Edge of the Transverse Sinus

Abstract

Even if image-guided methods have been used, surface landmarks are still important references in retrosigmoid craniotomy. The superior nuchal line (SNL) was thought to be roughly parallel to and below the lower edge of the transverse sinus (LETS). We intended to determine the relationship between the SNL and the LETS and verify the reliability of the SNL in locating the LETS. In total 72 human skull sides, the relationship between the SNL and the LETS was studied. The SNL was roughly parallel to and below the LETS in only 27 sides (37.5%) in our study. Totally, the SNL was roughly parallel to or just over the LETS in 81.9% of all sides. The SNL was obviously unparallel to the LETS in 13 sides (18.1%). Of the 13 sides, 6 difference types of relationship between the SNL and the LETS could be found. In our study, we got different result: the relationship between the SNL and the LETS seemed to be more variable; however, the SNL is still a useful surface landmark in retrosigmoid craniotomies. But considering the anatomic variability, it should be individualized by combining surface landmarks with image-guided methods.