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External carotid artery

The external carotid artery (ECA) is a major artery of the head and neck, supplying blood to structures of the face, scalp, jaw, neck, and some areas of the meninges. Arising from the common carotid artery at the level of the upper border of the thyroid cartilage, the ECA runs superiorly and slightly anteriorly, branching extensively to serve a wide territory. Understanding its anatomy and imaging appearance is crucial for clinicians, surgeons, and radiologists involved in head and neck assessment or interventions.

Synonyms

  • ECA

  • Arteria carotis externa (Latin)

  • External branch of the common carotid artery

Function

  • Supplies oxygenated blood to the face, scalp, neck, jaw, tongue, pharynx, larynx, and parts of the ear and dura mater.

  • Delivers blood to vital extracranial tissues, contributing to the vascular supply of the thyroid gland, oral cavity, nasal cavity, and maxillofacial region.

MRI Appearance

  • T1-Weighted (T1)

    • ECA lumen appears as a signal void (black) due to fast-flowing blood.

    • The vessel wall may be visualized as a thin, hypointense line.

    • Surrounding soft tissues (fat, muscle) provide anatomical reference.

  • T2-Weighted (T2)

    • ECA lumen also presents as a signal void because of flow-related dephasing.

    • Vessel walls are not usually visualized unless there is pathology.

    • Useful for assessing surrounding soft tissues for edema or mass effect.

  • STIR (Short Tau Inversion Recovery)

    • ECA remains a signal void.

    • This sequence suppresses fat and highlights edema in adjacent tissues, but does not provide direct detail of arterial lumen unless there is abnormality.

  • TOF (Time-of-Flight) MR Angiography

    • ECA appears as a bright, high-signal-intensity structure against a dark background.

    • Excellent for evaluating vessel patency, stenosis, or occlusion.

    • Visualizes the artery without need for contrast agents.

CT Appearance

  • Non-contrast CT

    • ECA is seen as a tubular, soft-tissue density structure.

    • Distinguishable from the internal carotid artery by location and course, but less specific than with contrast.

  • CT Angiography (CTA)

    • ECA is well-opacified with contrast, showing a bright, tubular appearance.

    • Enables precise visualization of the vessel's origin, course, branches, stenosis, plaques, and aneurysms.

    • Allows differentiation from adjacent veins and muscles.

MRI images

External carotid artery mri axial t2 image

CT image

External carotid artery CT axial image-img-00000-00000