Fig. 3.

( A ) The operculum of the endolymphatic sac ( dotted arrow ) is identified and serves as a guide for the lateral limit of dural dissection and bony removal. ( B ) The direct eight-nerve monitoring electrode is applied over the inferior aspect of the cochleovestibular bundle. Notice how it is secured in place with collagen sponges medially at the brainstem and laterally at the craniotomy edges. ( C ) Drilled out internal auditory canal demonstrating the vestibular nerves splayed over the posterior surface of the tumor.