Chapter 22

### Anatomy of Fascial Neck Planes & Spaces

The spatial compartments within the neck are defined by fascial planes. An understanding of this complex anatomy aids the clinician in diagnosing the cause of an infection and its likely routes of spread. Commonly affected spatial compartments are the retropharyngeal, parapharyngeal, and submandibular spaces.

The fascia of the neck comprises the superficial and the deep layers. The deep layer of cervical fascia is further divided into three layers: superficial, middle, and deep. The superficial portion of the deep cervical fascia envelops the sternocleidomastoid and trapezius muscles. It extends superiorly to the hyoid bone where it surrounds the submandibular gland and the mandible. Inferiorly, it attaches to the clavicle and, medially, it forms the floor of the submandibular space as it covers the muscles of the floor of mouth. The middle layer of deep cervical fascia, also known as the visceral or pretracheal fascia, surrounds the infrahyoid strap muscles, the thyroid, the larynx, the trachea, and the esophagus. Below the hyoid, this layer continues inferiorly to fuse with the pericardium. Above the hyoid, this layer continues on the posterior pharyngeal wall as the buccopharyngeal fascia. Between the middle and deep layers of deep cervical fascia is the retropharyngeal space.

The deep layer of cervical fascia, also known as the prevertebral fascia, surrounds the prevertebral muscle. Anteriorly, the deep layer of cervical fascia divides to form a thin alar layer and a thicker prevertebral layer. Between these two layers is the “danger space,” extending from the skull base to the diaphragm.

The submandibular space is bound in four ways: (1) anteriorly by the mandible, (2) superiorly by the mucosa of the floor of mouth, (3) inferiorly by the superficial layer of the deep cervical fascia, and (4) posteriorly by the parapharyngeal space. The mylohyoid muscle further divides this space into the submaxillary space (below the mylohyoid muscle) and sublingual space (above the mylohyoid muscle).

#### Essentials of Diagnosis

• Sore throat, dysphagia, odynophagia, and neck pain.
• Fever, trismus, and neck mass.
• CT scan with contrast, ring enhancement, scalloping of the abscess wall, or any combination of these findings.

#### General Considerations

Pharyngitis and dental infections are the most common causes of deep neck space infections. However, in a large portion of patients, the etiology is unknown. Other etiologies include salivary gland infections, trauma, intravenous drug use, and malignancy.

Deep space infections of the head and neck tend to follow the fascial planes of the neck. Controversy exists concerning the choices of empiric antimicrobial therapy, imaging modalities, and medical versus surgical treatment. The successful management of these potentially life-threatening infections depends on an understanding of the anatomy of the cervical fascial planes and spaces, bacteriology, and the potential complications that may arise.

#### Clinical Findings

##### Symptoms and Signs
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