The External Carotid Artery and the Styloid Process

The external carotid artery (ECA) is typically regarded as coursing between the styloid muscles to continue into the parotid space. The anatomical possibility of an ECA with an ascending parapharyngeal trajectory continuing posteriorly to an elongated styloid process (ESP), thus retrostyloid, to the parotid space is overlooked. It was, therefore, aimed to document the prevalence of this retrostyloid variant of the ECA's course.

We investigated a retrospective random cohort of 160 archived CT angiograms of 97 males and 63 females aged between 47 and 76. The presence of an ESP and the retrostyloid course of the ECA were bilaterally documented.

An ESP was identified in 99/320 sides (30.94%), regardless of the ECA course. In the overall group, we obtained 35% null cases for the two variables on the right and 34.06% for the left. ESPs were identified in 8.75% on the right side and 10.31% on the left. The ECAs had retrostyloid courses in 6.25% on the right side and 5.63% on the left. Thus, of the 320 ECAs documented on both sides, 221 (69.06%) had no retrostyloid courses, and we did not identify any ESP in those cases. ESPs were detected in 19.06% of the sides but without retrostyloid ECAs, and retrostyloid courses of the ECAs were detected in 11.88%.

The possibility of a retrostyloid course of the ECA should not be ignored. An ESP may misinform the surgeon about the main carotid artery located immediately deep to it.