The Pitfalls and Important Distances in Temporal Bone HRCT of the Subjects with High Jugular Bulbs - Preliminary Report

High jugular bulb (HJB) may be detected unilaterally or bilaterally in temporal bone high resolution computerized tomography (HRCT). In this retrospective study, we investigated the pitfalls and important surgical distances in patients with unilateral and bilateral HJB via temporal bone HRCT. In this preliminary report, the study group consisted of 20 adult patients (12 male, 8 female), or 40 ears, all of which underwent temporal bone HRCT. We divided them into groups that consisted of bilateral HJB (14 ears), unilateral HJB (13 ears), and control (No HJB, 13 ears). The anotomical relationships of the sigmoid sinus, jugular bulb, and carotid artery with several landmarks in the temporal bone were studied via temporal bone axial and coronal HRCT. The shortest distances between certain points were measured. These measurements were analyzed in respect to pneumatization. Dehiscence on the jugular bulb (JB) and internal carotid artery (ICA) and the dominance of JB were also evaluated for all of the groups. In the axial sections of the temporal bone HRCTs, the sigmois sinus (SS)-external auditory canal (EAC) distance of the bilateral HJB group (14.00±1.17 mm) was significantly lower than that of the control group (16.46±2.14 mm). The JB-posteromedial points of the umbo on the ear drum (ED) distance of the bilateral HJB (6.28±1.72 mm) and the unilateral HJB groups (7.23±2.00 mm) were significantly lower than that of the control group (11.15±2.30 mm). In the coronal sections of the temporal bone HRCT, the JB-F distance of the bilateral HJB group (5.42±2.10 mm) was significantly lower than that of the control group (8.30±2.28 mm). As the mastoid pneumatisation and mastoid volume increased, the percentage of ICA-dehiscence and the percentage of JB-dehiscence increased. In subjects with well-pneumatised mastoids, the doctors should be aware of the increased risk of ICA-dehiscence and JB-dehiscence. These measurements should be done in greater series to yield more thorough knowledge.