Imaging classification of jugular bulb variants on HRCT temporal bone and CT head and neck angiography: prospective...

Accurate imaging recognition of jugular bulb (JB) variants is essential for skull-base surgical planning and prevention of intraoperative vascular injury. This prospective study aimed to determine the prevalence and classification of JB variants using high-resolution CT (HRCT) temporal bone and CT head and neck angiography (CTA), evaluate the utility of standardized radiologic landmarks for consistent reporting and communication between radiologists and surgeons, and to assess associations with clinical symptoms and condylar canal size. A prospective observational study was conducted on 200 patients, including 100 undergoing HRCT temporal bone and 100 undergoing CTA performed for non-otologic indications. JB variants were classified using the Manjila-Semaan grading system based on internal auditory canal (IAC) and posterior semicircular canal (PSC) landmarks. Distances from the JB to key otologic structures, including the PSC, IAC, round window, basal turn of the cochlea, and vestibular aqueduct were measured. Associations with condylar canal size and clinical symptoms were analyzed using appropriate nonparametric and categorical statistical tests. Type 2 JBs were the most common, while high-positioned bulbs (Types 3 and 4) accounted for approximately 25%. Dehiscent bulbs were identified in 10% of cases. HRJB prevalence varied widely (7-32%) depending on the anatomical landmark used. No significant associations were found with age, sex or clinical symptoms. Condylar canal size demonstrated no significant correlation with JB size. JB variants, particularly high-riding and dehiscent forms, appear to be more prevalent than previously recognized. Standardized classification using IAC and PSC landmarks on multiplanar CT may improve reporting uniformity and facilitate communication between radiologists and skull-base surgeons. This prospective study also suggests that HRJB does not necessarily reflect compensatory enlargement of emissary venous channels and may instead represent focal venous remodeling independent of condylar canal size. Recognition of these variants is therefore important in preoperative planning to anticipate potential venous hemorrhage during skull-base surgery.