Embryonic Primary Head Sinus may Persist in the Petrosal Bone

Abstract

To report on unusual veins traversing the petromastoid part of the temporal bone (petrosal bone) and to discuss their embryological origins. Methods: Unusual veins traversing the petrosal bone were incidentally found on CTA, MRI, or conventional angiography in four cases. We have evaluated the course of these veins in detail and have reviewed the previous descriptions in the literatures about similar venous variations as well as the osseous and venous embryology around the petrosal bone. Results: In all cases, the vein was anteriorly connected to the dural venous sinus around the foramen ovale and entered the petrosal bone through the facial hiatus. With regard to the subsequent running course and its exit from the petrosal bone, the vein crossed the petrous internal carotid artery, exited the petrosal bone into the petroclival fissure, and entered the inferior petrosal sinus in two cases. In one case, the vein exited the petrosal bone through the stylomastoid foramen after running the entire length of the facial canal. In the remaining case, the vein ascended in the petrosal bone along its anterior aspect and emptied into the superior petrosal sinus. The running course of these veins may correspond to the course of the embryonic primary head sinus and its tributaries. Conclusion: Here we report on rare venous channels in the petrosal bone. We also believe that these veins may be remnants of the embryonic primary head sinus, based on their course in the petrosal bone and the embryological development of the veins in the region.