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1
Department of Pediatrics, CB 7220, 7701A 7th Floor, UNC Children's Hospital,
University of North Carolina, 101 Manning Dr., Chapel Hill, NC
27599-7200.
2
School of Medicine, University of North Carolina, Chapel Hill, NC
27599-7200.
3
Department of Radiology, University of North Carolina, Chapel Hill, NC
27599-7200.
4
Present address: Department of Radiology, Martha Jefferson Hospital, 459
Locust Ave., Charlottesville, VA 22902.
5
Trauma Outreach, University of North Carolina, Chapel Hill, NC
27599-7200.
Received December 14, 2000;
accepted after revision June 12, 2001.
M. C. Hollingshead was supported in part by training grant 5 T35 DK07386
from the National Institute of Diabetes and Digestive Diseases of the
Kidney.
Abstract
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MATERIALS AND METHODS. We identified 63 pediatric patients admitted to the emergency department who had head trauma and who underwent both head CT and neck radiography. Those who underwent CT of the cervical spine at the time of the head CT examination during their initial evaluation were compared for demographics, clinical status, mechanism of injury, and number of excess radiographs (number required by protocol minus number of films obtained) required to evaluate the cervical spine with those patients who did not undergo early CT of the cervical spine.
RESULTS. Twenty-one patients (33%) underwent cervical spine CT at the time of the head CT examination. The number of excess radiographs differed significantly between these patients (2.1 ± 2.6 vs 3.6 ± 2.7, p = 0.04) and the comparison group. Patients who did not undergo early CT for whom excess radiographs were obtained had the following characteristics: they were older than 8 years (p = 0.03), were unrestrained in a motor vehicle crash (p = 0.04), had a Glasgow coma score of 13-15 (p = 0.01), and were intubated (p = 0.02).
CONCLUSION. The number of repeated radiographs required to ascertain that the cervical spine is free of injury after suspected head trauma is significantly fewer when initial CT of the neck is performed at the time of head CT examination. Including cervical spine CT in trauma protocols for subgroups of children with head injuries may lead to more effective clearance of the pediatric cervical spine.
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Recently, performing CT of the cervical spine as an adjunct to radiography has led to a more efficient evaluation of the cervical spine in adult trauma victims [5]. Little is known about the use of CT for evaluating the cervical spine in pediatric victims of acute trauma. We hypothesized that performing CT of the cervical spine at the time of the head CT examination would decrease the number of excess radiographs required for pediatric trauma patients and make their treatment more efficient. To test this hypothesis, we compared the demographics, clinical status, mechanism of injury, and number of excess radiographs for patients who underwent cervical spine CT on initial evaluation with the same characteristics of patients who did not undergo initial cervical spine CT. "Excess radiographs" was defined as the number of repeated radiographs taken to ascertain that the cervical spine was injury-free that exceeded the number of radiographs required according to our standard protocol.
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In January 1999, pediatric patients with acute head trauma who underwent axial head CT and radiography of the neck also began undergoing cervical spine (C1-T1) CT (Somatom; Siemens, Erlangen, Germany) at the time of their head CT examination in addition to the routine radiography (the "early CT" group). Cervical spine helical CT was performed at a slice thickness of 3 mm and a pitch of 1. Images were reconstructed at 1.5-mm intervals with high-resolution bone algorithm and soft-tissue window settings. Images reviewed included the axial images and sagittal and coronal reformations presented at 1.5-mm thickness. The two groups of patients (those treated at our institution after January 1999, who underwent radiography and initial CT screening examination of the neck; and the control group, those treated before January 1999, who underwent only radiography of the cervical spine) were compared for demographic and clinical data. The groups also were compared for the number of excess radiographs. Flexion and extension images of the cervical spine requested to rule out ligamentous injury were not considered to be in excess. If a child received fewer than the required number of radiographs for cervical spine clearance, the number of excess radiographs was counted as zero. When calculating the specificity of conventional radiographs, radiographs having false-positive results were defined as those that incorrectly identified a fracture when none was present, that were incomplete, or that were inadequate and required CT follow-up.
Statistical analysis was done using the SPSS statistical package (Statistical Package for the Social Sciences, Chicago, IL) and Epi Info, version 6.0 (Centers for Disease Control and Prevention, Atlanta, GA). Descriptive information and relative risks were generated for demographic and clinical data. To determine if specific subgroups might benefit from the screening neck CT, we used the Student's t test to compare mean numbers of excess radiographs between groups. A multivariate logistic regression analysis was performed. A p value of 0.05 or less was considered significant.
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Twenty-one patients (33%) underwent cervical spine CT in addition to radiography at the time of the head CT examination to evaluate the cervical spine. Six (14%) of the 42 patients who did not undergo initial neck CT were unable to have their necks completely evaluated with radiography and went on to receive cervical spine CT later. Of the 63 patients who underwent radiography, six false-positive interpretations and one true-positive interpretation occurred in the early CT group, and six false-positive interpretations were noted in the non-CT group. Thus, the specificity of the radiography in this series was 81% [6] (Fig. 1A,1B,1C,1D).
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The two groups were similar in age and sex (Table 1). Clinical and injury characteristics (Table 1) did not differ significantly except that screening CT patients in the early group were more likely to have a Glasgow coma scale of 8-12 (19%) than control subjects (2.4%); however, these numbers were small. Patients who underwent CT of the neck on initial evaluation had significantly fewer repeated radiographs than patients who did not undergo early CT (mean, 2.1 ± 2.6 vs 3.6 ± 2.7 repeated radiographs, p = 0.04). Subgroup analysis (Table 2) showed that children 8 years old and younger and those who were unrestrained in a motor vehicle crash were likely to require an excess number of radiographs if they did not undergo early cervical spine CT. Children involved in a motor vehicle crash tended to undergo excess radiographs, but this number did not reach statistical significance (p = 0.07). Additionally, children who were not intubated, children without abnormalities on CT, and children with a Glasgow coma score of 13-15 were more likely to have more excess radiographs.
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When the mean cost (in United States dollars) of all radiologic studies performed to assess the cervical spine was analyzed for this high-risk group (involved in a motor vehicle crash and Glasgow coma score < 8), the cost for children who underwent early evaluation with cervical spine CT was not significantly different from the cost for those who did not ($997 ± $333 vs $776 ± $259, p = 0.2). The cost was equivalent between the two groups for those children with a Glasgow coma score of less than 8 regardless of mechanism of injury ($907 ± $341 vs $780 ± $236, p = 0.4). However, the cost for the entire cohort was greater for those undergoing early CT ($738 ± $320 vs $550 ± $305, p = 0.03) than for those who did not.
Children who underwent initial cervical spine CT did receive a higher effective dose of radiation (6.2 ± 2.2 mSv vs 3.2 ± 2.2 mSv, p < 0.001); however, children who had a Glasgow coma score of less than 8 and who underwent initial cervical spine CT at the time of head CT received equivalent doses of radiation (7.0 ± 2.2 mSv vs 5.6 ± 2.0 mSv, p = 0.15) compared with those children who did not undergo initial cervical spine CT, regardless of mechanism of injury.
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Involvement in a motor vehicle crash and a history of head trauma have been shown to be clinical markers of cervical spine injury in children [8]. The subgroup identified in our study that appeared to benefit from early CT also comprises those children at highest risk for cervical spine injury and those difficult to assess clinically because of a depressed level of consciousness and the need for intubation. In our cohort of patients, 40% of children were unable to undergo a full neurologic evaluation as a result of sedation and neuromuscular blockade.
Pediatric patients in general are at low risk for spinal injury. When injury does occur, it is associated with trauma of considerable force [9]. In a series of 34 children treated for cervical spine injury, the leading mechanism of injury was motor vehicle crash (68%) [10]. In that same series, head injury was associated with cervical spine injury in 53% of patients. The risk of performing cervical spine CT early in the child's evaluation is low. This cohort of children required head CT as part of their early management in the emergency department. Performing spine CT required only an additional short period of data acquisition; thus, no additional risk of morbidity was introduced by sedating children for the spine CT examination at a different session or by placing them in a less monitored setting.
The second subset of patients who appeared to benefit from early CT were those with lesser trauma. This subset included patients who were not receiving intubation, those with a Glasgow coma score of 13-15, and those with no abnormality on head CT. Possibly, this group of patients is less cooperative during radiography than the more severely injured group; thus CT, which is faster, may have a better chance of achieving a diagnostic study. With newer techniques such as multislice and electron beam CT, the examination time will conceivably be further reduced. However, children with a Glasgow coma score of 8 or more incurred significantly more cost and a higher dose of radiation than children who did not undergo initial cervical spine CT.
Our study found the specificity of radiography to be 81%, which is lower than the specificity found in a large adult trauma population. Blackmore and Deyo [11] reported a specificity of 89% for radiography in adult patients with head injury, which was significantly less than the specificity in all patients (96%; p = 0.03). This low specificity for radiography may be another reason to consider initial evaluation with cervical spine CT in high-risk pediatric patients.
Our study is limited in several ways. Because of its retrospective nature, we could not document whether the early screening cervical spine CT led to earlier clearance of the cervical spine and earlier removal of hard collars, because this information was not reliably recorded in the patients' charts. Additionally, because cervical spine injuries in children are rare [8], our sample size was too small to compare the efficacy of adjunctive cervical spine CT in detecting injuries. However, a recent study performed at a high-volume trauma center reported the sensitivity of helical CT in high-risk adult patients to be 95% (95% confidence interval, 90-100%) and the specificity to be 93% (95% confidence interval, 91-95%) [12].
Pediatric cervical radiographs can be difficult to interpret because of the developmental anatomy [13]. Detection of injury depends both on the quality of the radiographs and on the experience of the interpreter [14]. Adding CT to the evaluation of the spine adds another level of complexity that requires both equipment and interpretative skill. Therefore, the generalizability of using adjunctive CT may be limited. Although ours is a preliminary study, early evaluation with cervical spine CT in children at high risk for cervical spine injury does appear to be effective in decreasing the number of repeated radiographs necessary to assess the cervical spine. In this study, early evaluation with cervical spine CT did not add significantly to the cost or to the effective dose of radiation for the high-risk subgroup of children. Pending further studies, we recommend that children with a mechanism of injury that puts them at high risk for cervical spine injury, and for whom CT decreases the number of excess radiographs without increasing radiation exposure or cost, be considered for cervical spine CT at the time of head CT. These early results suggest that further prospective studies are warranted concerning the early use of cervical spine CT in selected populations of children with head injuries.
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  S. Ehara, C. J. Chung, and H. T. Keenan Limitations of CT Screening of Cervical Spine Injuries in Children Am. J. Roentgenol., August 1, 2002; 179(2): 533 - 533. [Full Text] [PDF]
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