Right transmastoid view of bony labyrinth and sigmoid sinus relationship. Bony removal of the mastoid process and retraction of cranial dura at the transverse-sigmoid sinus intersection reveals the entrance point of the superior petrosal sinus, the sigmoid sinus, and its continuation as the jugular bulb into the jugular foramen. Anterior to the sigmoid sinus is the bony labyrinth. The triangular area bounded by the bony labyrinth anteriorly, the sigmoid sinus posteriorly, and the superior petrosal sinus superiorly is known as Trautmann's triangle. (Image courtesy of AL Rhoton, Jr.)