Imaging;  Imaging head & neck trauma;  Penetrating and blunt neck trauma;  Radiography;  Radiology

Imaging of neck injuries encompasses all imaging-based methods by which patients with suspected or known traumatic neck injuries may be assessed including plain film radiography, fluoroscopic examinations, computed tomography (CT), magnetic resonance imaging (MRI), and catheter angiography.

Anatomic constraints within the neck result in close proximity of many vital structures. As such, trauma to this region may affect a single or multiple organ systems including injury to the aero-digestive tract, vasculature, and/or spine. Initial assessment of patients with suspected neck injury is aimed at identifying those who are unstable or exhibit clear evidence of vascular or aero-digestive tract injury as these individuals should proceed directly to surgical exploration without delay for imaging evaluation (Inaba et al. 2012). The possibility of cervical spine injury including fracture, dislocation, and/or cervical spinal cord injury should be considered in all cases of significant trauma as such injuries occur in 3–4 % of major trauma victims (Hasler et al. 2012). Traditionally, penetrating injuries are triaged according to the level of entry/exit wound. Injuries involving the neck from the level of the cricoid cartilage to the angle of the mandible (zone II) have traditionally undergone surgical exploration whereas imaging was pursued for injuries more cephalad or caudal to this level (zones I and III). Today, with the increasing availability and speed of imaging, most patients undergo imaging prior to surgery unless expedient treatment is necessary due to poor or declining patient stability.

Vascular and spinal injuries may be clinically occult, often due to the challenges of performing the neurologic exam in altered, sedated, or otherwise uncooperative trauma patients. Occasionally, vascular injuries manifest as a rapidly expanding neck mass; however, such cases are an exception rather than the rule. Most vascular injuries in the neck are not readily detectable on exam but rather clinically suspected based on the mechanism of injury or the presence of neurological deficit suggestive of cerebral infarction. Similarly, spinal injuries may manifest clinically; however, even in those with no obvious evidence of cord signs/symptoms, imaging screening for spinal injury is the currently accepted standard of care in patients who have sustained significant trauma.

Injury to the aero-digestive tract may occur as a result of blunt or penetrating trauma to the neck and may also be encountered as an iatrogenic injury related to endotrachael/enteric tube placement (Figs. 1 and 2) Such injuries may be suspected clinically in the presence of crepitus, hemoptysis, stridor, aphonia, loss of laryngeal prominence or hyoid elevation, certain injury patterns such as fracture of the first through third ribs, posterior sterno-clavicular dislocation, and/or detection of soft tissue emphysema on initially screening radiographic studies (Karmy-Jones et al. 2003; Sidell et al. 2011). Ensuring a viable airway is the primary management goal of treating patients with neck injury. Those with clinical signs of airway compromise and rapid decline should undergo emergent surgical tracheotomy. Less critical patients may undergo flexible laryngoscopy for management of the airway at the bedside (Sidell et al. 2011; Duval et al. 2007). Only after an adequate airway has been established should imaging be pursued.

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CT angiography (CTA) is recognized as the radiologic examination of choice for the workup of trauma patients with suspected vascular injury in the neck such as dissection or pseudoaneurysm (Figs. 3, 4 and 5). As an initial assessment tool, CTA allows triage toward conservative management versus intervention either endovascular or surgical (Stuhlfaut et al. 2005). As a result, the rate of surgical neck exploration including negative exploration has decreased over the past decade (Woo et al. 2005). Advantages of CT include wide availability, rapid scan times, and high (>95 %) sensitivity and specificity for the detection of clinically significant vascular and aero-digestive tract injuries to the neck (Inaba et al. 2012). Further, CTA of the neck may be performed in conjunction with CT evaluation of the chest and abdomen, thus negating the need for repeated contrast dosing.

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MRI/MRA may also be employed for the detection of carotid and/or vertebral artery dissection with sensitivity and specificity similar to that of CTA (Provenzale and Sarikaya 2009). The choice of imaging modality for potential dissection is thus typically based upon local practice patterns and patient specific factors. Advantages for MRI/MRA include improved detection of small infarctions and diffuse axonal injury when compared to CT. Additionally, for patients suspected of cervical cord injury, MR assessment of the extracranial cerebral vasculature may be included among the sequences acquired during a single although prolonged imaging session. Given the widespread availability of accuracy of noninvasive angiographic techniques, the role of conventional angiography lies mainly in cases of equivocal or discrepant results on CTA/MRA or for those in which high pretest suspicion for injury requiring endovascular intervention demands expedient evaluation and treatment (Provenzale and Sarikaya 2009).

When aero-digestive tract injury is suspected, CT examination of the neck and chest with contrast should be considered the examination of choice for detection and gross localization of the site of aero-digestive tract disruption within the neck and/or chest. Further, CT provides adding benefit of visualization of the vasculature, soft tissues, and osseous structures in the neck. Contrast esophagography, which is regarded as the gold standard radiologic examination for investigation of potential esophageal injury, is often challenging in patients who have sustained significant traumatic injury due to their inability to cooperate with the exam (Woo et al. 2005). In critically ill and intubated/sedated patients, video-endoscopy often allows detection of hypopharyngeal injuries that are notoriously difficult to identify via contrast esophagography as well as injuries of the cervical esophagus. For those patients who are able to cooperate for contrast fluoroscopic exams, several caveats must be considered. Due to the potential for fibrosing mediastinitis as a sequela of barium extravasation through a thoracic esophageal defect, water-soluble agents such as gastrograffin are used initially. Caution with these agents should be employed in patients at risk for aspiration due to the potential for pneumonitis. Given the improved sensitivity of thicker barium-based agents over water-soluble contrast, many radiologists advance to barium esophagography if no evidence of extravasation is seen with initial water-soluble swallows.

Non-enhanced CT of the spine is the current gold standard assessment tool to exclude cervical spine injury following trauma due to its superior depiction of osseous anatomy. In contrast, plain radiography has been shown to detect only 47–60 % of cervical spine fractures and fails to identify up to one third of potentially unstable cervical spine injuries (Hogan et al. 2005). For those with known cervical spine fracture or the clinical finding of spinal cord injury without radiographic abnormality (SCIWORA), MRI provides unparalleled assessment of intracanalicular and paraspinous soft tissues including the intervertebral disks, ligaments, and spinal cord (Figs. 6 and 7). Debate continues regarding the most appropriate management of the obtunded patient or in those otherwise unable to be cleared by neurological examination after negative cervical spine CT (Menaker et al. 2008). Factors include the benefits of early cervical collar removal in those patients whose MRI is negative versus the potential risks involved in transfer of potentially unstable patients to radiology for MR imaging. Multiple groups have examined the necessity of MRI in obtunded patients and concluded that MRI is not required on a routine basis in these patients (Hogan et al. 2005; Como et al. 2007; Soult et al. 2012). In support of these conclusions, cervical spine CT has negative predictive value of 98.9 % for ligamentous injury and 100 % for unstable cervical spine injury in patients following blunt trauma (Hogan et al. 2005). In contrast, literature also shows that MR of the cervical spine changes the management of 7.9 % of patients with an admission cervical spine CT reported as negative for acute injury (Menaker et al. 2008). Until conclusive data provided by large series is available, decisions regarding the merits of MR in the setting of a negative CT scan may be determined in large part by institutional and individual physician practices.

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