Episode 3

Soft Tissue Structures of the Neck

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the soft tissue structures of the neck are just as important as the bony spine. This is especially true when we consider trauma imaging. The potential for soft tissue injury from penetrating trauma, blunt trauma, forces associated with motor vehicle accident, and other types of trauma heighten the risk for soft tissue injury. By soft tissue structures we imply that in addition to the bony spine, all tissues within the boundaries delimited by skin (anteriorly, posteriorly, and laterally). These tissues include muscles, fat, the airway, esophagus, blood vessels, and the like. For our study we will only consider the airway and the carotid and vertebral arteries

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The airway is important to trauma because it must be maintained as part of the ABCs of survival (airway, breathing, and circulation). Radiographically, the injury to the airway or retropharyngeal space may indicate substantial trauma. Any deviation of the airway and other soft tissue structures may indicate a need for acute emergency treatment. It is necessary for the technologist to know some basic anatomy of the airway and identify its important features on a radiograph
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Fascial planes described in the neck

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Three fascial planes are described in the neck: investing, pretracheal, and prevertebral fascia. The investing fascia is a layer that encircles the structures of the neck. It is firmly attached to the mastoid processes, zygomatic arches, mandible, hyoid bone, and spinous processes, manubrium, clavicles, and both scapula. It is important because it contains the jugular venous arch and some muscles of the neck. 

Along the anterior portion of the neck is a thin layer of cervical fascia called the pretracheal fascia. It extends from the thyroid cartilage (C4) into the thorax. It is a split fascia which encloses the thyroid gland, trachea, and esophagus. Trauma to the trachea that results in a rupture of the trachea, or of a bronchus in the thorax can result in air seepage into the pretracheal fascial space. An acute swollen neck caused by air in the pretracheal fascia (mediastinal emphysema) may spread into the face along this route. 

The prevertebral fascia covers the muscles of the vertebral column, extending from the base of the skull to about the third thoracic vertebra. Its importance to us is that it is firmly attached to the anterior longitudinal ligament which can contribute to its injury from trauma. Because the pharynx is surrounded by a buccopharyngeal fascia there is a space created between it and the prevertebral fascia called the retropharyngeal space. This space contains the great vessels from the aortic arch, the heart, the trachea, the thymus and part of the esophagus. This space is important because it allows for movements of these structures, such as the esophagus during swallowing, and the beating of the heart. Trauma causing perforation into this space is radiographically significant; therefore, the radiographer must have an understanding of the dynamics of this anatomy so that it is included on routine plain films

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The picture above demonstrates the relative locations of the fascia, particularly noted is the retropharyngeal space, which is a potential space. Blood or pus that infiltrates into this space can spread to the superior mediastinum

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The airway
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The airway begins just posterior to the nasal and oral cavities with the pharynx. The pharynx is the upper respiratory tract, but is common to both the digestive and respiratory systems. It conducts food to the stomach via the esophagus, and air to the lungs via the trachea. The airway can be seen in the picture above. Visualization of the airway is important to imaging of the traumatic cervical spine.

Vertebral and carotid arteries

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There are four main arteries that pass through the neck in route to the brain to supply it with blood. These vessels are: the right and left vertebral arteries, and the right and left carotid arteries. An understanding of the gross anatomy of these vessels is important to radiographers because in certain types of trauma they could be injured. The goal of this brief review is to make the radiographer keener to the need of the patient toward other diagnostic test or surgery. It is not intended that the radiographer make a decision on patient care; however, valuable time should not be lost trying to get a good plain film radiograph when a CT scan may be quicker and more informative. An example would be to rule out a cervical spine injury from a fall, secondary to a gunshot injury. Now let’s consider the anatomy of these vessels.
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The carotids and vertebral arteries in the neck have their origins from the great vessels arising from the aortic arch in the superior mediastinum. 
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The blood supply to the brain from the neck is very important to survival because there are only four vessels that supply the entire brain with oxygenated nutrient rich blood. These vessels are the right and left vertebral arteries, and the right and left internal carotid arteries. Within the transverse foramina coarsens the right and left vertebral arteries in route to the brain supplying it with oxygenated blood. Each vertebral artery originates from its respective subclavian artery in the root of the neck (picture above). The vertebral arteries enter the transverse foramen of C-6 to ascend upward through the transverse foramina of C6-C1 entering the skull through the foramen magnum Through anastomoses these four vessels form contributories to the Circle of Willis supplying the brain with oxygenated blood. Any disruption in this supply can have grave consequences to the individual. Traumatic injury to these vessels can be evaluated by agiography, or in some cases with intravenous contrast CT angiography

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The bony spine protects the vertebral arteries; but only muscles and soft tissues of the neck protect the carotid arteries as the picture below shows. Injury to blood vessels like the carotids and vertebral arteries must be considered in certain types of traumatic injury to the neck or chest