Magnified view of the internal auditory canal. Within the internal auditory canal, a horizontal bony crest called the transverse crest separates the IAC into superior and inferior divisions, and a vertical bony crest called Bill’s bar further segments the IAC into quadrants. The facial nerve enters the superior anterior quadrant on its course to the geniculate ganglion along with the nervus intermedius. The cochlear nerve enters the inferior anterior quadrant. The superior and inferior vestibular nerves enter their respective posterior quadrants. (Image courtesy of AL Rhoton, Jr.)