Petrous bone

The carotid bifurcation can be seen in 80% of the adult population at the level of cervical vertebrae 3-5. Distal to the physiologic dilatation of the carotid bulb the internal carotid artery (ICA) proceeds dor-sally to the external carotid artery (ECA) into the petrous bone. Entering the bony carotid canal, it describes a sharp bend and thus causes turbulent flow patterns with somewhat typically symmetrical signal loss on TOF-MRA, which should not be misinterpreted as real stenoses (Fig. 5.2). 

The internal carotid artery starts as the carotid sinus at the bifurcation of the common carotid artery at the level of the thyroid cartilage. It runs up the neck, without any branches, to the base of the skull where it passes through the foramen lacerum to enter the carotid canal of the petrous bone. It then runs through the cavernous sinus in an S-shaped curve (the carotid siphon) pierces the dura and exits just medial to the anterior clinoid process. It then bifurcates into the anterior cerebral artery and the larger middle cerebral artery. 

In contrast to the reconstruction of the air, SR and VR also provide a global view of the petrous bone. Such a perspective can be useful in many situations to estimate bony alterations the malformation of the temporal bone that occurs in hemifacial mycro-somia, the surgical resection of bone performed in mastoidectomies, and the presence and extent of fractures. 

Guerrier Y, Guerrier B (1976) Topographic and surgical anatomy of the petrous bone. Acta Otorhinolaryngol Belg 30 22-50... 

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