Venous structures at the craniocervical junction: anatomical variations evaluated by multidetector row CT.

The aim of this study was to evaluate the anatomy of and normal variations in the craniocervical junction veins. We retrospectively reviewed 50 patients who underwent contrast-enhanced CT with a multidetector scanner. Axial and reconstructed images were evaluated by two neuroradiologists with special attention being paid to the existence and size of veins and their relationships with other venous branches around the craniocervical junction. The venous structures contributing to craniocervical junction venous drainage, including the inferior petrosal sinus (IPS), transverse-sigmoid sinus, jugular vein, condylar vein, marginal sinus and suboccipital cavernous sinus were well depicted in all cases. The occipital sinus (OS) was identified in 18 cases, including 4 cases of prominent-type OS. The IPS showed variations in drainage to the jugular vein through the jugular foramen or intraosseous course of occipital bone via the petroclival fissure. In all cases, the anterior condylar veins connected the anterior condylar confluence to the marginal sinus; however, a number of cases with asymmetry and agenesis in the posterior and lateral condylar veins were seen. The posterior condylar vein connected the suboccipital cavernous sinus to the sigmoid sinus or anterior condylar confluence. The posterior condylar canal in the occipital bone showed some differences, which were accompanied by variations in the posterior condylar veins. In conclusion, there are some anatomical variations in the venous structures of the craniocervical junction; knowledge of these differences is important for the diagnosis and treatment of skull base diseases. Contrast-enhanced CT using a multidetector scanner is useful for evaluating venous structures in the craniocervical junction.