Imaging in Whiplash

In the acute stage of whiplash injury, plain radiography is often the preferred imaging modality. The routine protocol for obtaining plain radiography varies from only lateral views in some centres, to three (anterior-posterior, lateral and open mouth view for frontal imaging of C1-C2), and to five views (adding right and left oblique projections) in other centres, with the five view plain radiography being the most adequate. Significant cervical spine injury can, however, be missed by plain radiography. Computed tomography (CT) has improved sensitivity for detecting fracture, and is shown to be faster and cost-effective in moderateand high-risk trauma patients. Modern multislice CT scanners provide 3D images of the cervical spine that are of excellent quality, with the possibility of reconstruction of images in multiple planes (Figure 1), and are increasingly replacing plane radiography in the acute stage. Magnetic resonance (MR) imaging has unique soft tissue discrimination ability and can diagnose injury in the paravertebral soft tissue, disk and cord, and is indicated when a neurological deficit is present or when there is clinical suspicion of a soft tissue or vascular abnormality. In moderateand high-risk acute cases, where the aim of imaging is to search for fractures, dislocation and instability, both the role and selection of imaging modality is uncontroversial. In the lowest risk group, both the United States National Emergency Utilization Study (NEXUS) and the Canadian C-spine Rule Study identified patients at risk for cervical injury, and aimed to avoid the unnecessary use of imaging. In chronic whiplash syndrome there is considerable controversy over the role of imaging. During recent years several publications have reported on CT and MR studies of the ligamentous structures between the head and the upper cervical vertebrae, with special emphasis on the alar ligament. Volle and colleagues have emphasized rotational instability, but these publications have inadequate method description, and diagnostic criteria and reliability measurements are missing. Pfirrmann and colleagues, however, found a high variation of segmental motion in the upper cervical spine in an asymptomatic population, and concluded that such measurements are unsuitable for an indirect diagnosis of soft tissue lesion after whiplash injury. The anatomical structures of these ligaments have been described in detail by Kraakenes and colleagues. Their study could detect the major ligamentous structures, including the alar ligaments, by the use of high-resolution protondensity-weighted MR sequences (Figure 2). The alar ligament was graded according to the presence of high signal intensity in the cross-section of the ligaments, and the presence of high signal intensity was reported to be related to whiplash injury. These findings have, however, not been verified by other groups. A study from my own institution demonstrated the same high signal intensity to be present in 15 healthy volunteers, and R Myran and colleagues found, in a randomized study of 173 subjects, the same high grade changes of the alar ligament among patients with chronic nontraumatic neck pain and healthy volunteers as among whiplash patients. The diagnostic value and the clinical relevance of high signal findings in the alar ligaments are, thus, unclear. Before implementing these findings in clinical practice, further research is absolutely essential. In conclusion, there is a role for cervical spine imaging in the acute stage of whiplash injury. In low-risk patients, imaging should be avoided, according to the NEXUS or Canadian C-spine Rule regimes. Plain radiography or CT is used to exclude fractures and dislocations, and MR of the neck should be performed when neurological deficits are