What are the branches of the external carotid artery (ECA)?

Branches of the External Carotid Artery

The external carotid artery (ECA) has eight major branches: superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary, and superficial temporal arteries. 1

Anatomical Overview

The external carotid artery originates at the bifurcation of the common carotid artery, typically at the level of the thyroid cartilage. From this point, it ascends through the neck and provides critical blood supply to structures of the face and neck through its eight branches.

Standard Branching Pattern

The eight major branches of the external carotid artery can be categorized by their direction:

1. Anterior Branches:

   • Superior thyroid artery: First branch, supplies the thyroid gland and larynx
   • Lingual artery: Supplies the tongue and floor of the mouth
   • Facial artery: Supplies facial structures including lips and nose

2. Medial Branch:

   • Ascending pharyngeal artery: Supplies the pharynx, middle ear, and meninges

3. Posterior Branches:

   • Occipital artery: Supplies the posterior scalp and neck muscles
   • Posterior auricular artery: Supplies the ear and surrounding area

4. Terminal Branches:

   • Maxillary artery: Supplies deep facial structures, sinuses, and teeth
   • Superficial temporal artery: Supplies the scalp and temporal region

Anatomical Variations

Several variations in the branching pattern of the ECA have been documented:

• Anterior Branch Variations: In approximately 80% of cases, the superior thyroid, facial, and lingual arteries originate independently (pattern I). However, in about 18% of cases, a linguofacial trunk may be present (pattern II), and less commonly, a thyrolingual trunk (pattern III) or thyrolinguofacial trunk (pattern IV) may occur 2.

• Posterior Branch Variations: The occipital and ascending pharyngeal arteries may originate independently or from a common trunk. In rare cases, either the ascending pharyngeal or occipital artery may be absent 2.

• Duplicate Branches: Cases of duplicate ascending pharyngeal arteries have been documented, which is clinically significant as this vessel supplies many skull base structures 3.

Clinical Significance

The anatomical knowledge of ECA branches is critical for:

1. Surgical Procedures: During head and neck surgeries, identification of these branches is essential to prevent inadvertent injury.

2. Endovascular Interventions: The ECA provides important collateral pathways to the brain through connections between its branches and cranial branches of the internal carotid and vertebral arteries. These collateral pathways become particularly important in patients with internal carotid artery occlusion 4.

3. Radiological Interpretation: Understanding the normal anatomy and variations helps in accurate interpretation of imaging studies of the head and neck region 5.

4. Reconstructive Surgery: Knowledge of the facial artery and its branches (superior labial, inferior labial, lateral nasal, angular, and submental) is crucial for planning and designing reconstructive flaps 6.

Important Collateral Pathways

The external carotid artery forms important collateral pathways to the brain through:

• Internal maxillary branch connecting to ophthalmic branches of the internal carotid artery
• Superficial temporal artery connecting to ophthalmic branches of the internal carotid artery
• Occipital branch connecting to the vertebral artery 1

These collateral pathways are crucial in cases of internal carotid artery stenosis or occlusion, as they can provide alternative routes for blood supply to the brain.

Clinical Pitfalls to Avoid

• Misidentification of ECA branches during surgical procedures
• Failure to recognize anatomical variations during interventional procedures
• Overlooking the importance of ECA collaterals in patients with cerebrovascular insufficiency
• Misdiagnosis of ascending pharyngeal artery anomalies as internal carotid artery dissection 3

Understanding these anatomical details and potential variations is essential for clinicians involved in the diagnosis and treatment of head and neck pathologies, as well as those performing interventional procedures in this region.