Unilateral Absence of Sigmoid Sinus

The sigmoid portion of the transverse sinus, although varying in position and in size in different mastoid processes, is, to be sure, a constant observation in temporal bones. The complete absence of this sinus, as shown in the following case report, is of interest not only because of its rarity, but because it serves to bring up the question of the embryology of the venous blood channels in the cranial cavity. REPORT OF CASE While dissecting a "head and neck" in the First Anatomical Institute of Vienna, Dr. Milton Golfein and I came across the following anomaly: The specimen was that of a man, aged 35, showing no apparent external deformity. After we had removed the brain and dura, our attention was directed to the disparity in size between the two petrous bones and the complete absence of a sigmoid sinus on the right side. Unfortunately, the dura had already