Helical CTA for Evaluation of Cervical Vascular Injury
Abstract & Commentary
Synopsis: Munera and associates report their initial experience with helical CT angiography in the examination of patients with penetrating neck trauma. They find that the sensitivity and specificity of helical CT angiography are high for detection of arterial occlusion, pseudoaneurysm, and arteriovenous fistula. They believe helical CT angiography may prove to be a good alternative to conventional angiography for the initial examination of patients with penetrating neck trauma, though larger clinical trials will be necessary to determine if helical CT angiography can replace conventional angiography in this setting.
Source: Munera F, et al. Diagnosis of arterial injuries caused by penetrating trauma to the neck: Comparison of helical CT angiography and conventional angiography.
Radiology 2000;216:356-362.
Penetrating injuries to the neck are associated with high morbidity and mortality rates owing to the high density of vital anatomical structures present within this anatomically small region. The diagnostic approach to the patient with a possible vascular injury is controversial, with potential avenues of assessment including close observation, conventional catheter angiography, or surgical exploration depending on the mechanism of injury, location of injury, and status of the patient. Noninvasive methods of vascular assessment have the potential to play a role in this setting. MR angiography is often not widely available in the acute setting, however, and the MR environment may not be appropriate for the acutely injured patient. Color Doppler ultrasound may also not be available in the acute setting, is operator dependent, and may be limited in those patients with large hematomas or subcutaneous emphysema. Munera and associates chose to determine the sensitivity and specificity of helical CT angiography (CTA) in the diagnosis of carotid and vertebral injuries caused by penetrating neck trauma.
The CTAs and catheter angiograms were assessed for vascular occlusion, pseudoaneurysm, arteriovenous fistula, and evidence of dissection. Source images from CTA studies were also assessed for fractures, soft tissue hematomas, or other nonarterial findings that could potentially be useful for patient care.
Ten (17%) of 60 patients had arterial injuries demonstrated at catheter angiography—seven in carotid arteries and three in vertebral arteries. Helical CTA demonstrated six of seven carotid injuries, with the "false-negative" study missing a small pseudoaneurysm at the origin of the common carotid artery that was not included in the imaging volume. All vertebral artery injuries were detected, and there were no false-positive CTA interpretations. Sensitivity of CTA was 90%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 98%. "Incidental" findings on CTA included fractures of the cervical spine and mandible, as well as large soft tissue hematomas causing compression of the airway.
Comment by Nancy J. Fischbein, MD
Patients who have sustained penetrating injuries to the neck and are hemodynamically unstable are usually taken directly to surgical exploration. The appropriate management of the hemodynamically stable patient with penetrating neck trauma, however, has been a source of controversy in the trauma literature.1, 2 With the advent of helical CT and the ability to rapidly acquire volumetric data sets that yield high-quality CT angiograms in most trauma centers, the question has been raised as to whether CTA can substitute for catheter angiography. While the numbers in this study are small, Munera et al demonstrate that a routine CTA acquisition that is post-processed rapidly using commercially available software has excellent sensitivity and specificity for cervical vascular injury. This study clearly suggests the need for a larger series to validate that a normal CTA does not require further angiographic evaluation, while an abnormal CTA would suggest catheter angiography or surgical exploration as the next step depending on the nature of the injury and whether endovascular therapy would be potentially appropriate. This situation is analogous to that of using CT to screen for aortic injuries with the hope of obviating arch aortography in the setting of blunt trauma, an approach that has been validated to some extent in recent years.3
Potential limitations of CTA include technical factors such as poor bolus timing or inadequate coverage (routine scanning should extend at least from the top of the aortic arch to the base of the skull with penetrating neck trauma); the requirement for iodinated contrast material; lower spatial resolution than conventional angiography; potential degradation of image quality from imaging artifacts (catheter angiography should be performed whenever the integrity of the whole length of the clinically suspicious artery or arteries cannot be seen be assessed fully by CTA); and the fact that therapeutic interventions cannot be performed immediately following diagnosis. There is also a requirement for timely and technically adequate post-processing. Whether these limitations prove to be significant will also need to be addressed with ongoing study.
References
1. Apffelstaedt JP, Muller R. Results of mandatory explo ration for penetrating neck trauma. World J Surg 1994;18:917-919.
2. Demetriades D, et al. Physical examination and
selective conservative management in patients with penetrating injuries of the neck. Br J Surg 1993; 80:1534-1536.
3. Nagy K, et al. Guidelines for the diagnosis and management of blunt aortic injury: An EAST Practice Management Guidelines Work Group. J Trauma 2000; 48:1128-1143.
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