Chapter 27

Knowledge of the anatomy of the neck is essential for both the diagnosis and the treatment of disease processes in the region. Contained within the neck are several triangles, defined anatomically (Figure 27–1). Familiarity with these specific areas assists in generating a differential diagnosis of neck masses by the exact anatomic location.

###### Figure 27–1.

Anatomic compartments of the neck.

The sternocleidomastoid muscle divides the neck into two major compartments, anterior and lateral.

### Anterior Neck

The following anatomic points define the anterior compartment of the neck: (1) the inferior border of the mandible superiorly, (2) the anterior border of the sternocleidomastoid muscle laterally, (3) the clavicle inferiorly, and (4) the vertical midline from mental symphysis to suprasternal notch medially. The structures that make up the anterior neck include the larynx, trachea, esophagus, thyroid and parathyroid glands, carotid sheath, and suprahyoid and infrahyoid strap muscles.

Triangular regions also define the anterior neck anatomically.

The submandibular triangle is a region contained in the anterior neck bordered by the inferior margin of the mandible and the digastric, stylohyoid, and mylohyoid muscles. This region contains the submandibular gland and the marginal mandibular branch of the facial nerve. The submental triangle defines a region bordered by the hyoid bone, the paired anterior bellies of the digastric muscles, and the mylohyoid muscle. The upper belly of the omohyoid muscle in the anterior neck further divides the anterior neck into an upper carotid triangle and a lower muscular triangle.

### Lateral Neck

The lateral neck, also referred to as the posterior triangle, is defined by the posterior aspects of the sternocleidomastoid muscle medially, the trapezius muscle laterally, and the middle third of the clavicle inferiorly. The lateral neck contains lymph node-bearing tissue, the spinal accessory nerve, and the cervical plexus. The inferior belly of the omohyoid muscle further defines a lower subclavian triangle in the lateral neck that contains the brachial plexus and subclavian vessels.

The differential diagnosis in a patient presenting with a neck mass is broad and extensive. Therefore, a thorough history and physical examination make up the critical first step in the evaluation of a neck mass. Information gathered from a detailed history and physical examination alone often narrows the differential diagnosis to a more manageable level (Figure 27–2).

###### Figure 27–2.

Evaluation of the neck mass in the adult.

### Patient History

The most important element in the evaluation of a neck mass is the age of the patient. Most pediatric neck masses are inflammatory or congenital and resolve spontaneously or after appropriate medical therapy. In contrast, a neck mass in an adult ...

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