An understanding of the applied anatomy of the neck includes a consideration of the layers of the deep cervical fascia and the compartments or spaces formed by the arrangement and attachments of these layers. This knowledge is crucial for planning treatment strategies and anticipating potential complications. The cervical fascia is divided into the superficial and deep fascia. The deep fascia is further subdivided into three layers or components: the superficial, middle, and deep. A summary of the organization of the cervical fascia is presented in Table 55.1
. Figure 55.1
features a midsagittal visualization of the fascia and deep neck spaces.
Superficial Cervical Fascia
The superficial cervical fascia lies beneath the skin of the head and neck, extending from the top of the head down to the shoulders, axilla, and thorax. This layer covers adipose tissue, sensory nerves, superficial vessels, lymphatics, the platysma muscle, and the muscles of facial expression. The platysma is absent in the midline. In contrast to the deep cervical fascia, which is composed of mainly fibrous connective tissue, the superficial cervical fascia is a layer of fibrofatty tissue connecting the overlying skin to the deeper fascial layers. Infections of this superficial space should be managed with appropriate antibiotic therapy in the case of cellulitis or extended to incision and drainage in the presence of an abscess (11
Deep Cervical Fascia
As noted earlier, the deep cervical fascia is a fibrous connective tissue layer that is, for surgical purposes, subdivided into the superficial, middle, and deep components. The appropriate designation for each layer is as follows: the superficial layer of the deep cervical fascia, the middle layer of the deep cervical fascia, and the deep layer of the deep cervical fascia. A practical observation is that layers overlying nonexpansile components such as the sternocleidomastoid muscle (SCM) are well-developed membranes that can be sutured. On the other hand, fascia surrounding expansile visceral organs such as the pharynx and cheeks is a loose areolar tissue, not amenable to suture retention. Additionally, muscles and organs within these layers are generally free to glide upon contraction and relaxation.
The superficial layer of the deep cervical fascia, also referred to as the investing layer, completely surrounds the neck. The superior nuchal line, ligamentum nuchae of the cervical vertebrae, and the mastoid process are the posterior attachments. The fascia splits to envelope the sternocleidomastoid and trapezius muscles as it courses anteriorly. In the anterosuperior direction, an attachment is made to the inferior zygomatic arch. Moving inferiorly, the parotid gland is enveloped superficially, while the deep extent involves the carotid canal of the temporal bone. The stylomandibular ligament, which separates the parotid and submandibular glands, is formed as this investing fascia tracks anteriorly to cover the submandibular gland and muscles of mastication. The inferior extent includes attachments to the hyoid, acromion, clavicle, and scapular spine. The suprasternal space of Burns is formed as the fascia surrounds the intermediate tendon of the omohyoid muscle. This space may contain a lymph node along with a vessel bridging the two anterior jugular veins (12
). A useful tool in understanding the contents of this plane is the “rule of two’s,” referring to the two muscles above the hyoid bone (masseter and anterior belly of the digastrics), two muscles that cross the neck (trapezius and SCM), two salivary glands (parotid and submandibular), and two fascial compartments (parotid and masticator spaces) (11
The middle layer of the deep cervical fascia, also called the visceral fascia, is divided into a muscular and visceral division. The muscular division of the middle layer of the deep cervical fascia surrounds the sternohyoid, sternothyroid, thyrohyoid, and omohyoid strap muscles. Contents of the visceral division include the parathyroid glands, thyroid gland, esophagus, trachea, larynx, pharyngeal constrictor muscles, and buccinator muscle. This visceral division further contributes to two additional planes: the pretracheal fascia and buccopharyngeal fascia. The pretracheal fascia overlies the trachea. The buccopharyngeal fascia lies posterior to and separates the esophagus from the deep layer of the deep cervical fascia. This plane also marks the anterior border of the retropharyngeal space. The buccinators, pharyngeal constrictor muscles, and esophagus lie between the pharyngobasilar fascia anteriorly and the buccopharyngeal fascia posteriorly (12
). The two raphes formed by the buccopharyngeal fascia include the posterior midline raphe, which attaches to the alar layer of the deep layer of the deep cervical fascia, and the pterygomandibular raphe within the lateral pharynx (11
). Portions of the middle layer of the deep cervical fascia that surround the trachea and esophagus merge with the fibrous pericardium in the superior mediastinum, representing a possible portal of spread of infection.
The deep layer of the deep cervical fascia, also known as the prevertebral fascia, is composed of two divisions as well: the prevertebral and alar divisions. The prevertebral division contains the cervical vertebra, phrenic nerve, and paraspinous muscles. This fascia runs from the skull base to the coccyx, forming the anterior wall of the prevertebral space, with lateral and posterior attachments to the transverse spinous processes, respectively. The clinical significance of this boundary is the confinement of primary vertebral infections to the prevertebral space with very limited spread to the danger space. The alar division is situated between the prevertebral division posteriorly and the buccopharyngeal fascia of the visceral division of the middle layer of the deep cervical fascia anteriorly, separating the retropharyngeal and danger spaces. This layer extends from the skull base to the second thoracic vertebra. The notable structure within this plane is the cervical sympathetic trunk. In reviewing the deep fascial and special relationships within the neck, the following structures are encountered as one goes from anterior to posterior: the pharyngobasilar fascia, the esophageal or constrictor musculature, the buccopharyngeal fascia of the visceral division of the middle layer of the deep cervical fascia, the retropharyngeal space, the alar division of the deep layer of the deep cervical fascia, the danger space, the prevertebral division of the deep layer of the deep cervical fascia, the prevertebral space, and finally the vertebral body (12
The carotid sheath is formed by contributions of all three layers of the deep cervical fascia, extending from the skull base to the thorax. Contents of this sheath include the common carotid artery, internal jugular vein (IJV), vagus nerve, and ansa cervicalis (11