Walsh & Hoyt: Internal Carotid Artery and Its Branches

The cervical segment of the ICA begins at the level of the bifurcation of the CCA. This segment runs inside the carotid sheath and ascends behind the tonsillar fossa to the base of the skull and enters the cranial cavity by passing through the carotid canal. The next segment of the ICA lies within the carotid canal of the petrous bone and is called the petrous segment. Two branches may arise from the petrous segment of the ICA, the caroticotympanic artery and the vidian (pterygoid) artery. The ICA then exits from the petrous bone superiorly to enter the cavernous sinus.