Vestibulocochlear Nerve

The cisternal and canalicular segments of the facial nerve and the vestibulocochlear nerve are invested in a common arachnoid sheath. This chapter discusses some of the important gross variations of the vestibulocochlear nerve. Proximal stem of the vestibulocochlear nerve, close to the pons, may give rise to the rootlets of the intermediate nerve of Wrisberg. In 22% of cases, the intermediate nerve adheres to the vestibular part of the vestibulocochlear nerve along its cisternal course. The anterior inferior cerebellar artery (AICA) may cross the vestibulocochlear nerve inferiorly, posteriorly, anteriorly, or between it and the facial nerve. The meatal loop of AICA establishes a variable relationship with the vestibulocochlear nerve. The gross segmentation of the vestibulocochlear nerve into its division is not clear in the cisternal segment, but this becomes evident beginning from the porus or midportion of the internal acoustic meatus.