View of the left mastoid region after petrosectomy. For orientation, the left side of the image is caudal. The left mastoid bone has been drilled to reveal the mastoid air cells just posterior to the external auditory meatus and middle ear. The dura over the sigmoid sinus remains intact. The digastric muscle originates in the digastric notch just posterior to the tip of the mastoid. The occipital artery courses over the obliquus capitus superior muscle prior to sending a branch intracranially. The V3 segment of the vertebral artery is visible in the suboccipital triangle between the obliquus capitus superior and obliquus capitis inferior muscles. In this view, visible branches of the external carotid artery including the internal maxillary artery and posterior auricular artery are dissected. (Image courtesy of AL Rhoton, Jr.)