Left presigmoid exposure of the lower cranial nerves. The sigmoid sinus is retracted medially but is tethered by the superior petrosal sinus, which runs along the petrous ridge from the cavernous sinus to drain into the transverse sinus at its junction with the sigmoid sinus. Cranial nerve IV is visible coursing in close relationship to the edge of the tentorium. Cranial nerve V emanates from the anterolateral pons toward Meckel’s cave within the trigeminal depression on the temporal bone. Cranial nerves VII and VIII form a complex entering the internal acoustic meatus and inner ear, along with the labyrinthine artery. The semicircular canals of the inner ear are visible. Cranial nerves IX and X are visible here in close relationship to the posterior inferior cerebellar artery (PICA). (Image courtesy of AL Rhoton, Jr.)