Right posterior view of drilled internal auditory canal. The facial, nervus intermedius, and vestibulocochlear nerves are shown entering and traversing the internal auditory canal. A loop of the anterior inferior cerebellar artery appears at the meatus. The nerves segregate into quadrants at the fundic region by partitions formed by shelves of bone. The transverse or falciform crest creates a superior compartment containing the facial and superior vestibular nerves and an inferior compartment for the cochlear and inferior vestibular nerves. The vertical crest or Bill's bar divides the superior compartment into an anterosuperior quadrant for the facial nerve and a posterosuperior quadrant for the superior vestibular nerve. While no similar crest exists inferiorly, conceptually, the cochlear nerve occupies the anteroinferior quadrant and the inferior vestibular nerve the posteroinferior quadrant.