TraumaVertebral artery injury after blunt cervical trauma: an update
Introduction
Until recently, VAI after blunt cervical trauma has been considered to be rare. Although the condition itself has been known long before, it was only after early 1990s that seriousness of the issue began to be realized among spine surgeons [9], [16], [19], [51], [58], [61], [63], [75], [91]. Numerous clinical studies that investigated the incidence, clinical/radiological characteristics, therapeutic interventions, and outcomes ensued within the last decade, which revealed that VAI after blunt cervical trauma actually occurred more frequently than had been thought [6]. Vertebral artery injury has been underdiagnosed or misdiagnosed frequently, mainly because many VAI patients remain asymptomatic if the VA is damaged only unilaterally. On the other hand, misdiagnosed VAI has often been reported to cause acute neurologic deterioration of previously conscious patients with cervical spine injury [11], [33], [64]. Heightened awareness of spine surgeons has contributed to a detection of many asymptomatic VAI patients who would otherwise be undiagnosed. There still have been controversies, however, particularly regarding what the best imaging modality or treatment for patients with VAI is [2]. The authors aim to update the recent findings on this subject by a review of the literature.
Section snippets
Methods
A comprehensive review of the pertinent articles published between 1990 and 2004 was made. The publications were searched and retrieved via PubMed, with key words used such as cervical, dissection, injury, occlusion, spinal cord, spine, trauma, vascular, and vertebral artery. In this review, “trauma” is usually used to mean the act of external noxious impact, whereas “injury” is used to mean the condition resulting from trauma.
Incidence
The incidence of VAI may vary significantly, depending on whether asymptomatic patients are diagnosed accurately. A severe blunt cervical trauma, such as a MVA, is more likely to cause not only cervical spine injury but also extensive soft tissue injury and VAI. On the other hand, even a minor blunt cervical trauma, such as chiropractic manipulation, aerobics, or yoga, is known to cause VAI, which is dissection in most instances, without significant cervical spine injury [18], [47], [56], and
Mechanisms of injury
In general, vascular injury after blunt cervical trauma results either from shearing forces secondary to rotational injuries or from direct trauma to the vessel wall from bony prominences or fragments [6], [61], [91]. Distraction/extension, distraction/flexion, and lateral flexion injuries (classification by Allen et al [1]) have been implicated as major mechanisms of injury in VAI [6], [53], [61], [77], [91].
Vertebral artery injury associated with significant cervical spine injury, which
Type of vascular injury
Types of vascular injury after blunt trauma include dissection with or without an intimal flap or mural thrombus, pseudoaneurysm, occlusion, transection, and AVF [6]. The intima is the most vulnerable anatomic structure in the vascular wall, and its disruption results in dissection. Progression of dissection to involve the media, coupled with formation and accumulation of thrombus, results in stenosis or complete occlusion [66]. The adventitia is relatively resistant to traumatic stress, but
Spine injury patterns predictive of VAI
Several specific cervical spine injury patterns closely associated with VAI have been documented. Fractures extending into the transverse foramen, into and through which the VA courses from C6 to C1, had a high incidence of VAI [15], [49], [85], [89], [91], [93]. In a retrospective study of 216 patients with cervical spine fractures, transverse process fracture was present in 24%, and in 78% of them, the fracture extended into the transverse foramen [93]. It is obvious from anatomy that bony
Neurologic manifestation
Because of a rich collateral circulation in the neck, most unilateral VAI patients remain asymptomatic [66]. Even acute occlusion of the dominant-side VA does not always result in neurologic deficits [5], [7]. Only 12% to 20% of unilateral VAI patients initially presented with symptoms and signs of vertebrobasilar ischemia [5], [48]. Neurologic manifestations of VAI were protean and included quadriplegia or paraplegia not compatible with the level of known cervical cord injury, dizziness,
Imaging studies
Digital subtraction angiography has been the most sensitive imaging modality to describe the types and degree of vascular injury, and many authors have considered it to be a criterion standard with which other imaging modalities should be compared [5], [6], [7], [24], [38], [43], [48], [49], [62]. Subtle intimal irregularities can be detected only with DSA. Immediate therapeutic intervention is possible after a diagnostic angiography, particularly in cases with transection or AVF [25], [78]. It
Treatment
There have been controversies regarding the treatment strategy for patients with VAI, particularly for those who remain asymptomatic. There is little room for argument, however, whether symptomatic VAI patients need treatment. Transection of the VA after a blunt cervical trauma is a rare but life-threatening condition. Patients presents with hemorrhagic shock and/or obliteration of the airway due to a rapidly expanding neck hematoma [30]. Emergency neuroradiological intervention with
Conclusion
Heightened awareness of spine surgeons has contributed greatly to the early diagnosis and increased incidence of VAI. Rapid refinement in diagnostic imaging technology is expected to improve the diagnostic sensitivity and specificity of MRA and CTA as comparable with that of DSA in the near future. Early treatment of asymptomatic VAI with heparin or antiplatelet agents seems to be gaining popularity and is expected to decrease the number of unexpected vertebrobasilar strokes. No clinical
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