Improved CT Imaging for Mastoid Emissary Vein Visualization Prior to Posterior Fossa Approaches.

Background  The clinical relevance of emissary veins (EVs) is often neglected. However, for posterior fossa approaches, especially in semisitting positions, these transosseous connections become potentially life threatening. Therefore, knowledge of the presence and configuration of EVs is essential in preoperative planning. We report on the use of preoperative computed tomography (CT) imaging techniques to visualize EVs reliably. Methods  A total of 100 consecutive patients were evaluated by helical CT in bone window mode reconstructed using the standard technique (4.5-mm slices) and the high-resolution technique (1 mm) for the posterior fossa. The presence and size of the EVs, their entry point in the sigmoid sinus, their predilection site, and their visibility using either CT technique were evaluated. Statistical analyses included a comparison of the data from both sides of the head. Results  We noted impressive anatomical variations (high standard deviations) in the number, size, and intraosseous length of the EVs among the study population and between the sides (right and left) of an individual patient; however, no statistical significance was observed for any of these parameters. The detection rate of EVs in thin-slice CT scans versus standard CT scans is significantly different ( p  = 0.0001 on both sides). Conclusions  Thin-slice CT is essential in the preoperative planning of posterior fossa approaches to identify the presence and the course of EVs, reducing preventable approach-related morbidity during surgery.
(Georg Thieme Verlag KG Stuttgart · New York.)