Neck Trauma 

Few emergencies pose as great a challenge as neck trauma. Because a multitude of organ systems (eg, airway, vascular, neurological, gastrointestinal) are compressed into a compact conduit, a single penetrating wound is capable of considerable harm. Furthermore, seemingly innocuous wounds may not manifest clear signs or symptoms, and potentially lethal injuries could be easily overlooked or discounted.

Airway occlusion and exsanguinating hemorrhage pose the most immediate risks to life. From the time when Ambroise Pare successfully treated a neck injury in 1552, debate has continued about the best approach for particular neck wounds. Awareness of the various presentations of neck injuries and the establishment of a well-conceived multidisciplinary plan prior to the traumatic event is critical for improving patient outcome.

A clear understanding of the anatomic relationships within the neck and the mechanisms of injury is critical to devising a rational diagnostic and therapeutic strategy.

Structures at risk

With the neck protected by the spine posteriorly, the head superiorly, and the chest inferiorly, the anterior and lateral regions are most exposed to injury. The larynx and trachea are situated anteriorly and are therefore readily exposed to harm. The spinal cord lies posteriorly, cushioned by the vertebral bodies, muscles, and ligaments. The esophagus and the major blood vessels are between the airway and spine.

Two fascial layers invest the neck: the superficial fascia (enveloping the platysma muscle) and the deep cervical fascia. The deep cervical fascia envelops the sternocleidomastoid and trapezius muscles as well as demarcates the pretracheal region (including the trachea, larynx, thyroid gland, and pericardium), the prevertebral area (containing the prevertebral muscles, phrenic nerve, brachial plexus, and axillary sheath), and the carotid sheath (enclosing the carotid artery, internal jugular vein, and vagus nerve).

Musculoskeletal structures at risk include the vertebral bodies; cervical muscles, tendons, and ligaments; clavicles; first and second ribs; and hyoid bone.

Neural structures at risk include the spinal cord, phrenic nerve, brachial plexus, recurrent laryngeal nerve, cranial nerves (specifically IX-XII), and stellate ganglion.

Vascular structures at risk include the carotid (common, internal, external) and vertebral arteries and the vertebral, brachiocephalic, and jugular (internal and external) veins.

Visceral structures at risk include the thoracic duct, esophagus and pharynx, and larynx and trachea.

Glandular structures at risk include the thyroid, parathyroid, submandibular, and parotid glands.

Associated structures at risk of intrathoracic injuries include the esophagus, tracheobronchial tree, lung, heart, and great vessels.

Anatomic zones

Dividing the neck into anatomic zones or regions assists in the evaluation of injury. Serving as the line of demarcation, the sternocleidomastoid separates the neck into anterior and posterior triangles. Most of the important vascular and visceral organs lie within the anterior triangle bounded by the sternocleidomastoid posteriorly, the midline anteriorly, and the mandible superiorly. Except for individual nerves to specific muscles, few vital structures cross the posterior triangle, which is delineated by the sternocleidomastoid, the trapezius, and the clavicle (with the exception of the region just superior to the clavicle).

For clinical purposes, the neck is partitioned into 3 zones (as is shown in the image below).

Zone I (as is illustrated in the image below), the base of the neck, is demarcated by the thoracic inlet inferiorly and the cricoid cartilage superiorly.

Structures at greatest risk in this zone are the great vessels (subclavian vessels, brachiocephalic veins, common carotid arteries, aortic arch, and jugular veins, trachea, esophagus, lung apices, cervical spine, spinal cord, and cervical nerve roots. Signs of a significant injury in the zone I region may be hidden from inspection of the chest or the mediastinum.

Zone II (as is illustrated in the image below) encompasses the midportion of the neck and the region from the cricoid cartilage to the angle of the mandible.

Important structures in this region include the carotid and vertebral arteries, jugular veins, pharynx, larynx, trachea, esophagus, and cervical spine and spinal cord. Zone II injuries are likely to be the most apparent on inspection and tend not to be occult. Additionally, most carotid artery injuries are associated with zone II injuries.

Zone III (as is seen in the image below) characterizes the superior aspect of the neck and is bounded by the angle of the mandible and the base of the skull.

Diverse structures, such as the salivary and parotid glands, esophagus, trachea, vertebral bodies, carotid arteries, jugular veins, and major nerves (including cranial nerves IX-XII), traverse this zone. Injuries in zone III can prove difficult to access surgically.

Penetrating trauma

More than 95% of penetrating neck wounds result from guns and knives, with the remainder resulting from motor vehicle accidents, household injuries, industrial accidents, and sporting events. Generally, people experiencing a gun shot wound (GSW) sustain greater injury than those with stab wounds because of a bullet's proclivity to penetrate deeper and cause cavitation, thus damaging structures lying outside the tract of the missile.^[1]

High-velocity bullet wounds (>2000-2500 ft/s) tend to follow a direct and predictable pathway, while low-velocity bullets travel a more erratic pathway, often demonstrating no direct relationship to the entrance or exit wounds. Additionally, high-velocity bullet wounds produced by military-style weapons or hunting rifles generate shock waves that devitalize surrounding tissues. High-velocity missiles and their ensuing blast effects may suck debris into the wound tract or cause secondary injuries from bullet or bone fragmentation. Low-velocity injuries may be produced by .22-caliber and .38-caliber handguns that have a muzzle speed of 300 ft/s to 800 ft/s. Furthermore, lower-energy injuries (knife, handgun, long-range birdshot or buckshot) cause a 50% lesser frequency of clinically significant injuries no matter what the zone of injury.

A lateral transcervical GSW is more likely to cause a grave injury than a GSW involving injury to only one side of the neck. Close-range GSWs of the neck that produce massive destruction are usually fatal. After a GSW to the neck, surgery is indicated in 75% of cases, whereas only 50% of neck stab wounds require surgical exploration.

Vascular injuries arising from penetrating trauma may occur directly, causing a partial or complete transection of the vessel or inducing formation of an intimal flap, arteriovenous fistula, or pseudoaneurysm. Injury to the blood vessels can also result from external compression or mural contusion. Thrombosis is the most common complication of blood vessel injury, occurring in 25-40% of patients.

The internal jugular vein (9%) and carotid artery (7%) are the most common sites of vascular injuries. Injury to the pharynx or the esophagus occurs in 5-15% of cases. The larynx or the trachea is injured in 4-12% of cases. Major nerve injury occurs in 3-8% of patients sustaining penetrating neck trauma. Spinal cord injury occurs infrequently and almost always results from direct injury rather than secondary osseous instability.

Blunt trauma

Blunt trauma to the neck typically results from motor vehicle crashes but also occurs with sports-related injuries (eg, clothesline tackle), strangulation, blows from the fists or feet, and excessive manipulation (ie, any manual operation such as chiropractic treatment or physical realignment or repositioning of the spine).

In motor vehicle crashes in which the driver is not belted, the driver is in danger of thrusting forward with the head extended, forcing the anterior neck against the steering column. Shoulder harnesses appear to offer some, though incomplete, protection against blunt neck trauma; cerebral vessel and laryngeal injuries secondary to shoulder strap compression have occurred.

Nonpenetrating trauma can injure a blood vessel through a multitude of mechanisms.

Direct forces can shear the vasculature. Excessive rotation and/or hyperextension of the cervical spine causes distention and stretching of the arteries and veins producing shearing damage and resultant thrombosis. Intraoral trauma may extend to the cerebral blood supply. Basilar skull fractures may disrupt the intrapetrous portion of the carotid artery. Impact to the exposed anterior aspect of the neck may crush the larynx or the trachea, particularly at the cricoid ring, and compress the esophagus against the posterior spinal column. A sudden increase in intratracheal pressure against a closed glottis (eg, improper wearing of a seat belt), a crush bruise (eg, clothesline tackle), or a rapid acceleration-deceleration action may cause a tracheal injury.

Strangulation may result from hanging (partial or complete suspension of the body from the neck), ligature suffocation, manual choking, and postural asphyxiation (eg, seen in children when the neck is placed over an object and the body weight produces compression). Significant cervical spine and spinal cord damage happens in only those hangings that involve a fall from a distance greater than the body height. Simple asphyxiation is not the major cause of death in hanging injuries. Cervical spinal disruption subsequent to strangulation is almost uniformly fatal.

Frequency

United States

Neck trauma accounts for 5-10% of all serious traumatic injuries. Approximately 3500 people die every year from neck trauma secondary to hanging, suicide, and accidents.

Mortality/Morbidity

During the Vietnam era, when mandatory exploration and vascular repair was the standard of care for penetrating neck wounds, the mortality rate for the civilian population was 4-7%. Today, the overall mortality rate has decreased to 2-6%. Recent studies from Operation Iraqi Freedom reveal the perioperative mortality rate and the positive exploration rate for high-velocity penetrating neck trauma by deployed surgeons are very comparable to those rates seen in civilian centers managing low-velocity penetrating neck trauma.^[2]

Initially missed cervical injuries secondary to neck trauma result in a mortality rate of greater than 15%. Ten percent of neck wounds lead to respiratory compromise. Loss of the airway patency may occur precipitously, resulting in mortality rates as high as 33%.

Zone I injuries are associated with the highest morbidity and mortality rates.

Sex

Trauma is more common among males than among females.

Age

Most people who experience neck trauma are adolescents and young adults.