Role of ethnicity in the determination of the transverse sigmoid sinus Junction (TSSJ): A prospective hospital-based radiological study in adult Sabah, East Malaysia

The Transverse Sigmoid Sinus Junction (TSSJ) is a critical anatomical landmark in neurosurgery, particularly in cerebello-pontine angle (CPA) procedures. Despite its significance, there is limited research on the anatomical variations of the TSSJ, particularly regarding ethnic differences. This prospective radiological study aims to investigate the potential influence of ethnicity on the anatomical differences of the TSSJ in the adult participants from Sabah. This prospective hospital-based cross-sectional radiological study included 180 adult patients who underwent high-resolution CT imaging, comprising various races. Participants were categorized based on ethnicity, and detailed radiological data were collected to analyze the variations in the TSSJ across different ethnic groups. Participants recruited were between the ages of 22 and 80 and were divided into 3 major ethnic groups. The anatomical landmarks used in this study include the asterion, internal auditory canal, cranial index, and ‘key point’. Preliminary findings revealed notable variations in the TSSJ among ethnic subgroups within the Sabah participants. Measurements of key anatomical points demonstrated differences that may have implications for safe burr hole placement in CPA surgery. It was observed that the left asterion to key point was higher compared to the right, with males having significantly higher asterion to key point, key point to IAC, vertical distance of key point to IAC, and cranial index (p < 0.001), respectively. In terms of race, asterion to key point (p = 0.020), key point to IAC (p = 0.039), and cranial index (p < 0.001) were observed to be significant. Post hoc analysis revealed that Chinese had significantly higher asterion to key points than ‘others’ (p < 0.001), and the cranial index for ‘others’ was considerably lower than Malay, Chinese, and Kadazan (p < 0.001). There is valid evidence to support ethnic-specific external landmarks in surgical practice, which is important for locally practicing neurosurgeons.