ABSTRACT
I have discussed the “side-by-side” rotated variation of ICA and ECA earlier in the text, and I have emphasized the special positioning of the patient needed in such a case (see Figs. 2-3 and 3-4). These two operative photographs of a right carotid exposure demonstrate the side-by-side anatomy and the risk of becoming confused if the situation is not appreciated. Before taking the pictures I marked the arteries as C, I, and E, meaning common, internal, and external carotids respectively. In (A), one can see that the internal carotid artery is medially rotated and basically out of view. By dissecting along the lateral border of the carotid tree the surgeon can deliver the ICA laterally and create a more normal anatomical picture, as has been done and illustrated in (B). The risk, of course, is that an inexperienced surgeon will mistake the ECA for the ICA, and thus do extensive dissection medial to the ECA, looking for an ICA there that will never be found. There are two ways to avoid this error: first, by understanding and expecting the variant based on the angiogram, and second, by always using the landmark of the superior thyroid artery to identify the ECA.
