Computed Tomography Detection of Accessory Foramen in the Jugular Foramen: Implications for Skull Base Surgery

Accurate anatomic knowledge of the jugular foramen (JF) is essential in skull base surgery, where morphologic variations—particularly ossified dural septations—can significantly impact surgical planning and outcomes. A recently described variant, the accessory foramen (AF) located on the inferior surface of the JF, may represent such ossified septations. This study aimed to assess the radiologic presence of AF using high-resolution computed tomography (CT). A retrospective analysis was conducted on 168 high-resolution head CT scans (336 sides). Scans were reconstructed in three dimensions (3D) and analyzed using multiplanar reconstructions (MPR). AF was identified unilaterally in 6 patients (3.6% 6/168 patients; 1.8% of sides). All cases were visualized via 3D reconstruction (3DR), while MPR delineated the variation in only 2 cases. Accessory foramen appeared more frequently on the left side (P=0.099), with no significant association with sex (P=0.936) or age (P=0.893). The mean diameter of the AF was 2.41±0.49 mm. This study confirms the presence of a rare AF likely resulting from ossified dural septations, detectable in vivo via 3D CT reconstruction. Recognition of this variant holds important neurosurgical implications, enabling enhanced preoperative assessment and reducing the risk of lower cranial nerve injury during skull base procedures.