Mastoid Emissary Vein Canal Incidence and Its Relationship with Jugular Bulb and Sigmoid Sulcus Anatomical Variations

Objective: We aimed to investigate the mastoid emissary vein (MEV) canal incidence and to identify its relationship with jugular bulb (JB) and sigmoid sulcus anatomical variations. Methods: We retrospectively reviewed 1,300 patients with temporal bone computed tomography (CT) scans in January 2016 to March 2020. The presence and the diameter of the MEV canal, and the anatomical variations of the sigmoid sulcus and the JB were reviewed by two radiologists. High riding JB, JB diverticulum, dehiscent JB, and anterior and lateral protrusion of the sigmoid sulcus were evaluated. All variables were summarized using descriptive statistics. The differences between the groups for categorical data were investigated using the chi-square test. Numeric variables were compared with the Mann-Whitney and the Kruskal-Wallis tests. Logistic regression models were constructed. Results: The study included 1,269 patients of whom 694 were female (54.7%) and 575 were male (45.3%). Their mean age was 39.01±18.47. Among them 915 (72.1%) had the right and 871 (68.6%) had the left MEV canal. Men were more likely to have the MEV canal on both sides. The presence of the right and left MEV canals was associated with the ipsilateral dominant JB/sigmoid sulcus. The left MEV canal was associated with the left high riding JB and right dehiscent JB. Conclusion: This is the largest patient population reported in the literature and allows a more precise estimate of the MEV canal incidence. We also classified the diameter of the MEV canal to identify clinically relevant, prominent MEV incidence. This is also the first study to demonstrate a relationship between the presence of the MEV canal, and the JB and sigmoid canal variations. Since both the prominent MEV and the JB variations may be symptomatic, knowing this association between them may have clinical relevance.