The External Carotid Artery and the Styloid Process

Area of Science:

• Anatomy
• Vascular Surgery
• Radiology

Background:

• The external carotid artery (ECA) typically travels between styloid muscles to the parotid space.
• A retrostyloid course of the ECA, posterior to an elongated styloid process (ESP), is an overlooked anatomical variant.
• Understanding ECA trajectory variations is critical for surgical planning and avoiding misidentification of vessels.

Purpose of the Study:

• To determine the prevalence of the retrostyloid variant of the external carotid artery's course.
• To document the association between the retrostyloid ECA and the presence of an elongated styloid process.

Main Methods:

• Retrospective analysis of 160 CT angiograms (97 male, 63 female, aged 47-76).
• Bilateral documentation of elongated styloid process (ESP) presence and retrostyloid ECA course.
• Analysis of 320 carotid artery sides for anatomical variations.

Main Results:

• An elongated styloid process (ESP) was identified in 30.94% of sides.
• Retrostyloid courses of the external carotid artery (ECA) were observed in 6.25% on the right and 5.63% on the left.
• A combined analysis revealed retrostyloid ECA courses in 11.88% of documented sides.

Conclusions:

• The retrostyloid trajectory of the ECA is a significant anatomical possibility that should not be disregarded.
• An elongated styloid process (ESP) can potentially mislead surgeons regarding the location of the internal carotid artery.
• Awareness of this variant improves surgical safety and accuracy in head and neck procedures.