<p>The sigmoid sinus (SS) exhibits significant anatomical variation, influencing surgical access to critical regions of the temporal bone. Understanding its relationship to surrounding structures is essential in otologic and skull base procedures. To assess the anatomy and variations of the sigmoid sinus in relation to the posterior semicircular canal and presigmoid plate in cadavers, and to evaluate its radiological position relative to the external auditory canal. This cross-sectional observational study involved 30 wet cadaveric temporal bones. Radiological measurements were obtained using Schüller’s view of X ray mastoid, and anatomical measurements were made during microscopic dissection. Distances between the SS and posterior wall of the external auditory canal, mastoid tip prominence, pneumatization type, and SS grading were recorded. Data was analyzed using Epi Info 7.2. The mean radiological and anatomical distances from the SS to the posterior EAC wall were 2.91 ± 0.85&#xa0;mm and 2.20 ± 0.82&#xa0;mm, respectively (<i>p</i> = 0.56). Prominent mastoid tips were observed in 80% of cases. Pneumatization types were equally distributed (30% each for pneumatic, diploic, and sclerotic; 10% mixed). Grade 2 sigmoid sinus positioning was most common (40%). A significant association was noted between poor pneumatization and anteriorly placed sigmoid sinus (<i>p</i> = 0.001). The sigmoid sinus demonstrates high anatomical variability. Intermediate-risk (grade 2) sinus positioning is most frequent. Reduced mastoid pneumatization is significantly associated with anteriorly placed sigmoid sinus. Preoperative imaging is essential for surgical planning to minimize complications.</p>