The anatomical relation of the extracranial internal carotid artery in the parapharyngeal space

Background. The proximity of the internal carotid artery to the pharyngeal wall poses a risk of injury during nasopharyngeal surgery. Objectives. The aim of this study was to assess the distances between the extracranial internal carotid artery (ICA) and the pharyngeal wall. Material and methods. Measurements were taken on certain levels of the pharynx using computed tomography angiography (angio-CT) scans of 97 patients. One-tailed Student's t-test for independent variables and a comparison of expected values for dependent pairs of observations were applied. Results. The shortest distance between the ICA and the pharyngeal wall was 1.1 mm. The ICA is closer to the pharyngeal wall at the epiglottis apex level (16.46 +/- 0.89 mm) than to the Eustachian tube (ET) (19.8 +/- 0.62 mm) (p < 0.0005). In women, the ICA is closer to the ET (19.44 +/- 0.78 mm) than in men (20.17 +/- 0.96 mm) (p = 0.04). In women, the right ICA is closer to the pharyngeal wall than the left ICA at the level of the lower margin of the 2nd cervical corpus vertebra (C2) (right: 17.6 +/- 1.8 mm; left: 20.7 +/- 1.7 mm) (p = 0.002) and at the level of the epiglottis apex (right: 15.2 +/- 1.7 mm; left: 17.4 +/- 1.4 mm) (p = 0.028). The bifurcation of the common carotid artery (CCA) is higher in men (19.48 +/- 2.19 mm below the C2) than in women (21.82 +/- 1.02 mm) (p < 0.001). When the bifurcation is at the level of the epiglottis apex, the ICA is closer to the pharyngeal wall (12.3 +/- 1.69 mm) than in other cases (16.46 +/- 0.89 mm) (p = 0.005). In men, the higher the bifurcation is, the closer the ICA is to the pharyngeal wall at the level of the lower margin of the C2 (p = 0.003). Conclusions. The risk of ICA incision during surgery differs between the pharyngeal levels, genders and sides of the neck. The ICA may be much closer to the pharyngeal wall than described in the literature.