View of cerebellopontine area following mastoidectomy. For orientation, the left border is superior, the right border is inferior, the top border is anterior and the lower border is posterior. Anteriorly, one can observe the mastoid segment of the facial nerve descending within the facial canal. From this segment, the chorda tympani arises and enters the middle ear cavity. In a rostral-caudal sequence, the motor and sensory roots of the trigeminal nerve leave and enter the pons, respectively. The facial nerve and nervus intermedius and superior and inferior vestibular nerves converge on the internal auditory meatus. The abducens nerve emerges from the pons further inferiorly and medially. The glossopharyngeal and vagus nerves can be seen leaving the medulla and coursing toward the jugular foramen. Within the dura mater, the sigmoid sinus is in view posteriorly and continues inferiorly as the jugular bulb before giving rise to the internal jugular vein at the jugular foramen. (Image courtesy of AL Rhoton, Jr.)