(8,9) This case likely represents a prominent basilar venous plexus in the retroclival region, which is not commonly seen on CT or MR imaging, or possibly a prominent inferior petro-occipital vein, which has been described in the literature.
Cohen-Gadol, "Anatomy of the inferior petro-occipital vein and its relation to the base of the skull: application to surgical and endovascular procedures of the skull base," Clin Anat, vol.