Fig. 6.

Presigmoid versus retrosigmoid trajectories. ( A ) Extensive dissection of a neuroanatomic specimen centered on the lateral skull base and sigmoid sinus region highlights the relative trajectories afforded by retrosigmoid (*) versus presigmoid (**) approaches to the CPA. Although the dura forming Trautman's triangle between the sinus, bony labyrinth, and superior petrosal sinus has been removed, the very high position of the jugular bulb in this specimen would markedly limit a presigmoid approach in a patient with similar anatomy. ( B ) Comparable dissection of a different neuroanatomic specimen demonstrates how a patient with a low-lying jugular bulb would constitute a more appropriate candidate for presigmoid in addition to retrosigmoid approaches. CPA, cerebellopontine angle.