Incidence

Cervical vessels are involved in 25% of head and neck trauma, and carotid artery injury constitutes 5%³ of all arterial injuries. Penetrating injury is the leading mechanism of injury, with gunshot wounds accounting for half of them, while blunt trauma comprises less than 10%,⁴ most of them due to motor vehicle crashes. Mortality still has been very high, ranging between 10% and 30%, with an incidence of permanent neurologic deficit of 40%.⁵

Mechanism of Injury

Carotid artery injuries usually result from high-velocity missiles or direct impacts to the head. While high-velocity missiles may injure directly or by concussive forces, or cause secondary injury by bone fragments, low-velocity missile injuries are confined to the missile tract. Blunt injuries may result from direct impacts to the vessel causing disruption of the wall or as a result of bony fragments from associated injuries.⁶ Motor vehicle crashes account for the majority of blunt neck injuries. Drivers and passengers on motorcycles, bicycles, jet skis, and snowboards can also sustain blunt neck injuries from direct impact.⁷

In order to provide a guideline in the management of penetrating neck injuries, the wounds to the neck have been grouped into three separate zones: zone I, injuries from the clavicle to the cricoid cartilage; zone II, injuries between the cricoid and angle of mandible; and zone III, injuries above the angle of mandible and the base of the skull.⁸

Of the three zones of the neck, zone II is the easier to expose via an incision parallel to the anterior border of the sternocleidomastoid muscle. Zone I often requires a median sternotomy for the more proximal portions of the common carotid artery. In zone III, the internal carotid artery is approached by extending the sternocleidomastoid incision to the ear into the postauricular space.

Diagnosis

Physical examination of patients with traumatic neck injuries is of paramount importance. The importance is confirmed by the fact that vascular injuries of the neck are associated with mortality rates up to 30% and are present in approximately 25% of all neck injuries. Signs such as expanding hematoma of the anterior or posterior triangle of the neck, audible cervical bruit, palpable thrill, abrasions on the neck secondary to seatbelts, and neurological deficits, are highly suggestive of a vascular injury of the neck. Additional findings include ipsilateral Horner’s syndrome, active bleeding from oropharyngeal wounds, cranial nerves IX to XII deficits, and a diminished pulse in the ipsilateral superficial temporal artery.

Color-flow duplex (CFD) has emerged a valuable and accurate tool in the assessment of traumatic vascular injuries. Numerous studies have documented the accuracy CFD in the diagnosis of cervical vascular trauma, especially in zone II injuries to the neck.^9–15 When performed by a trained technologist and interpreted by a practitioner familiar with the nuances of flow disturbances, CFD correlates with contrast angiography in over 90% of zone II carotid injuries. Color-flow duplex has the advantage of being noninvasive and does not require contrast agents, thus making in-hospital follow-up examinations safe. Unfortunately, due to the adjacent bony structures, CFD is not useful in diagnosis of zone I and III injuries. Also, because the accuracy of CFD is so highly dependent on the personnel performing and interpreting the study and the availability of the personnel is variable after hours, use of CFD is limited even in trauma centers with Level 1 distinction. As usage of emergency-room ultrasound imaging increases in the secondary assessment of intracavitary trauma patients, extension of the scanning to include the neck may become commonplace. Color-flow capability of the ultrasound machine and appropriate training for acute care practitioners would be required.

With advances in the speed of acquisition and the enhanced software allowing elaborate reconstructive views, computerized tomography angiography (CTA) has become more commonly used as a diagnostic modality in traumatic neck injuries. With many patients already being evaluated with CT scans of the cervical spine, chest, and abdomen, CTA has the advantage of not requiring additional transport of the critically injured patient. This is especially the case in head-injured patients where a CT scan of the head is crucial to evaluate the existence of concurrent intracranial hematomas, parenchymal brain injury, or cerebral edema; here CTA of the neck to screen for extracranial and intracranial major vascular trauma is efficacious. In comparing CTA to CFD, Mutze and associates¹⁶ demonstrated that CTA was more sensitive in detecting blunt carotid injuries and recommended contrast material-enhanced studies to avoid the morbidity of a missed cervical vascular injury. Unfortunately, CTA requires the use of nephrotoxic contrast agents to adequately delineate the vascular anatomy, which, when combined with the contrast load required for scanning of the chest and abdomen, increases the possibility of renal toxicity in the hemodynamically compromised trauma patient.

Magnetic resonance arteriography (MRA) is a viable imaging tool to evaluate the extracranial and intracranial vasculature; however, application to trauma patients is not widely accepted. MRA shares the advantage of CTA in that other areas can be imaged simultaneously and in being noninvasive, but unlike CTA, MRA uses a non-nephrotoxic contrast agent. Miller and colleagues¹⁷ prospectively screened selected patients for blunt cerebrovascular injuries and compared the diagnostic modalities, CTA, and MRA, and contrast angiography (CA) in 143 trauma patients. Compared to CA, MRA and CTA had sensitivities of 50% and 47%, respectively, for carotid artery injuries. Similar results were demonstrated for blunt vertebral artery screening with MRA and CTA having respective sensitivities of 47% and 53%. Based on their findings, these authors cautioned against routine use of these modalities for screening of cervical vascular injuries. Compounding this report is the fact that MRA is not easily accessible in the majority of hospitals, and the presence of metallic orthopedic instrumentation limits widespread usage for trauma patients.

Contrast angiography still remains the gold standard with which all other diagnostic modalities are compared. This is especially true in zones I and III vascular injuries where accurate definition of the vascular pathology is essential to planning operative approaches. With the advent of endovascular surgery, CA has the distinct advantage of being the only diagnostic modality where treatment of the vascular abnormality can be rendered immediately after the diagnosis is established.

Treatment

Surgical reconstruction remains the mainstay therapy for carotid arterial injuries. Ligation, a treatment option of the past, is only reserved for cases of extensive injury or life-threatening exsanguination. In patients with signs of extensive pulsatile hemorrhage, expanding hematomas with or without airway compromise, immediate surgical exploration is recommended. Neurological evaluation should always be document prior to surgical intervention. Despite having a dense neurological deficit preoperatively, surgical repair is still recommended. Weaver and associates¹⁸ demonstrated that regardless of the initial neurological deficit, mortality and final neurological status improved after surgical arterial repair. Since this report, subsequent studies documented similar success with surgical repair.^19,20

Despite the success of operative intervention, nonoperative management of carotid injuries is justified in certain clinical scenarios. For example, in patients diagnosed with a carotid artery occlusion, a significant neurological deficit, and a large cerebral infarct on the ipsilateral side, observation is the preferred treatment of choice due to the poor prognosis in this subgroup of patients. Similarly, in patients with carotid artery occlusion and a normal neurological examination, observation and anticoagulation therapy for a period of at least 3 months is recommended to avoid any propagation of existent thrombus.

Likewise, patients diagnosed with “minimal” vascular injuries based on CFD or CA do not require as aggressive surgical approach. Minimal injuries can be described as nonobstructive or adherent intimal flaps and pseudoaneurysms less than 5 mm in size. Initial work by Stain and coworkers²¹ documented the safety of observation in 24 nonocclusive arterial injuries. Patients in this study were managed nonoperatively and subsequently studied arteriographically at 1–12 weeks after injury. Resolution, improvement, or stabilization of the injury occurred in 21 injuries (87%). Progression was noted in three, and only one required repair. There were no cases of acute thrombosis or distal embolization. Later, Frykberg et al.²² documented a similar report with data extending to 10 years with comparable excellent results, thus confirming the wisdom of this approach.