Anatomical study of petrous and cavernous parts of internal carotid artery

The petrous and cavernous parts of internal carotid artery (ICA) are obscure and are not readily accessible to observation/imaging. These parts have broad biological and medical interest because of their peculiar shape. Given the their clinical importance and the scarce data available based mostly on imaging, the present study was aimed at studying these parts of ICA by dissection. The study was carried out on 56 ICAs obtained from embalmed adult cadavers and 10 ICAs from five fetuses. The foetal ICAs were studied in situ. The morphometric analysis of the adult ICA was done after its removal from cranial cavity to gain an insight into the geometry of the vessel, i.e., length, various bends, and diameters at various locations. ICAs in fetuses ran a relatively straighter course taking gentle curves at three positions (two intrapetrous, one cavernous). Adult ICAs were more tortuous and exhibited greater variability in length and angulations. The length of respective portions of the ICA correlate negatively with the measure of angles. The angles in the petrous and cavernous parts were positively correlated to each other. The carotid siphon was positively, highly significantly correlated to other angles. Longer vessels are more tortuous with acute bends. An acute carotid siphon is an indication of more tortuous ICA. The findings of the present study have created a reference data of unsuspected adult population and has potential implications for studying cause/effect relationship of vessel geometry and hemodynamic factors.