Background: Ruling out injuries of the cervical spine in obtunded blunt trauma patients is controversial. Although computed tomography (CT) readily demonstrates fractures and malalignment, it provides limited direct evaluation of ligamentous integrity, leading some to advocate a magnetic resonance imaging (MRI) in obtunded patients. Thus, the question remains: does adding an MRI provide useful information that alters treatment when a CT scan reveals no evidence of injury?
Methods: Published studies from 2000 to 2008 involving patients undergoing MRI for the purposes of further cervical spine evaluation after a "negative" CT scan were identified via a literature search of online databases. Data from eligible studies were pooled and original scale meta-analyses were performed to calculate overall sensitivity, specificity, positive and negative predictive values, likelihood ratios, and relative risk. The Q-statistic p value was used to evaluate heterogeneity.
Results: Eleven studies met the inclusion criteria, yielding data on 1,550 patients with a negative CT scan after blunt trauma subsequently evaluated with a MRI. The MRI detected abnormalities in 182 patients (12%). Ninety traumatic injuries were identified, including ligamentous injuries (86/182), fractures, and dislocations (4/182). In 96 cases (6% of the cohort), the MRI identified an injury that altered management. Eighty-four patients (5%) required continued collar immobilization and 12 (1%) required surgical stabilization. The Q-statistic p value for heterogeneity was 0.99, indicating the absence of heterogeneity among the individual study populations.
Conclusions: Reliance on CT imaging alone to "clear the cervical spine" after blunt trauma can lead to missed injuries. This study supports a role for the addition of MRI in evaluating patients who are obtunded, or unexaminable, despite a negative CT scan.