Epidemiology of blunt head injury victims undergoing ED cranial computed tomographic scanning

American Journal of Emergency Medicine (2006) 24, 167 – 173

www.elsevier.com/locate/ajem

Original Contributions

Epidemiology of blunt head injury victims undergoing ED cranial computed tomographic scanningB James F. Holmes MD, MPHa,*, Gregory W. Hendey MDb, Jennifer A. Oman MDc, Valerie C. Norton MDd, Gerald Lazarenko MDe, Steven E. Ross MDf, Jerome R. Hoffman MA, MDg, William R. Mower MD, PhDg, for the NEXUS group1 a

Department of Emergency Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA Department of Emergency Medicine, UCSF Fresno Medical Education Program, Fresno, CA 93702, USA c Department of Emergency Medicine, UC Irvine College of Medicine, Irvine, CA 92868-3298, USA d Department of Emergency Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-4700, USA e Department of Emergency Medicine, Foothills Medical Centre, University of Calgary, Canada T2N 2T9 f Division of Trauma, Department of Surgery, Cooper Health Systems, Camden, NJ 08103, USA g Division of Emergency Medicine, UCLA School of Medicine, Los Angeles, CA 90024-1777, USA b

Received 14 June 2005; revised 23 July 2005; accepted 18 August 2005

Abstract Study Objective: We sought to describe the epidemiology of emergency department (ED) patients with blunt head injury undergoing cranial computed tomography (CT) scanning for the evaluation of possible traumatic brain injury (TBI). Methods: Prospective, multicenter, observational study of ED patients undergoing cranial CT after blunt head injury. Patient’s date of birth, sex, and race/ethnicity were documented before CT scanning. Individual patients were considered to have bsignificant Q TBI if the official radiographic interpretation at the end of all imaging studies associated with the trauma was consistent with any of a set of predefined diagnoses. The relative prevalence of TBI among various prespecified groups from those undergoing cranial CT scanning was also calculated. Results: Of 13 728 patients who were enrolled, 8988 (65%) were men and 1193 (8.7%) had a significant acute TBI. Demographic findings associated with increased risk of TBI, among patients selected for scanning, included the following: age below 10 years (relative risk [RR] = 1.44, 95% confidence interval [CI], 1.19 -1.77); age above 65 years (RR = 1.59; 95% CI, 1.40 -1.80), and male sex (RR = 1.27; 95% CI, 1.30 -1.43).

B

This work was funded by Grant no. 1 RO1 from the Agency for Health Care Policy and Research and Quality, Rockville, MD. T Corresponding author. Division of Emergency Medicine, UC Davis Medical Center-PSSB 2100, Sacramento, CA 95817-2282, USA. Tel.: +1 916 734 1533; fax: +1 916 734 7950. E-mail address: [email protected] (J.F. Holmes). 1 The centers and investigators that collaborated in this study are listed in the appendix. 0735-6757/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.ajem.2005.08.009

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Conclusion: Among patients selected for cranial CT scanning after blunt head injury, men, patients younger than 10 years, and those older than 65 years have an increased likelihood of significant TBI. D 2006 Elsevier Inc. All rights reserved.

1. Introduction Most patients seeking medical attention after blunt head trauma initially present to an emergency department (ED) for evaluation [1]. Although significant traumatic brain injury (TBI) occurs in only 5% to 10% of all patients with blunt trauma, TBI is associated with high levels of morbidity and mortality [2 - 5]. Previous epidemiologic studies of patients with TBI have focused on admitted patients, special populations, or population-based studies [5 -15]. The spectrum of subjects in such studies likely differs from that seen in most EDs, and thus, such reports may be of only limited use to emergency physicians. To determine the prevalence, spectrum, and distribution of significant TBI, we prospectively enrolled all blunt trauma victims undergoing cranial computed tomography (CT) at 21 diverse institutions. The objective of this substudy from the National Emergency X-Radiography Utilizations Study (NEXUS) group was to describe the epidemiology of ED patients undergoing cranial CT scan after blunt head trauma.

2. Methods NEXUS-II is a prospective, observational study performed at 21 different EDs. A detailed description of the NEXUS methodology is available elsewhere [16]. The NEXUS study enrolled all patients undergoing cranial CT scanning after blunt head trauma. Participating centers represented a wide range of EDs, including those of university hospitals, community hospitals with and without teaching programs, public hospitals and private hospitals, and hospitals with all levels of trauma categorization. Data collection forms were completed on all patients undergoing cranial CT scanning as part of their ED evaluation. The decision to obtain cranial CT imaging was made by the managing ED physician in each case, based on his or her clinical judgment, and was not influenced by the ongoing study. Patients with penetrating injury and those undergoing cranial CT scanning for a nontraumatic indication were excluded. The study population thus consists solely of patients with blunt trauma evaluated in the ED who underwent cranial CT scanning to determine the presence or absence of TBI. Institutional review board approval was obtained at each study site. Data collection forms were completed by the managing physicians before knowledge of the cranial CT scan results. Information was collected on the subjects’ dates of birth, race/ethnicity, sex, and results of cranial CT imaging. All

cranial CT scans were interpreted by board-certified/eligible radiologists at the individual study sites. The diagnosis of TBI was based solely on the final radiological interpretation of all imaging studies, including any radiographs subsequently obtained in the inpatient setting. Clinically significant TBI was defined before data collection and listed in Table 1. Isolated linear or basilar skull fractures, small cerebral contusions, and coincidental or congenital abnormalities were not considered to represent significant traumatic brain injuries. A chronic subdural hematoma without evidence of acute change was not considered to be a significant acute injury. Study investigators reviewed all ambiguous reports to determine the final injury classification of these patients. This review was conducted while masked to any information about clinical variables. Injury information was then concatenated with clinical data to form the final study database. Data analysis was conducted with Stata statistical software (Stata, College Station, TX). Continuous variables are reported as the mean F 1 SD or median with interquartile ranges (IQRs). Relative risk (RR) ratios were calculated to determine risk of TBI for specified groups. 95% confidence intervals (CIs) are calculated for RR ratios and measurements of prevalence.

3. Results The study enrolled 13 728 patients with blunt head trauma. One thousand one hundred ninety-three (8.7%; 95% CI, 8.2% -9.2%) patients had significant TBI, as

Table 1

Clinically significant traumatic brain injuries

Epidural hematoma Subdural hematoma Cerebellar hematoma Intracerebral hematoma Subarachnoid hemorrhage Intraventricular hemorrhage Multiple cerebral contusions Single cerebral contusion N2 cm in diameter Traumatic infarction Pneumocephalus Depressed or complex skull fractures Complex skull fractures Diastasis of the skull Diffuse cerebral edema Chronic subdural hematoma with any recent change

Epidemiology of blunt head injury victims

Fig. 1

Number of enrolled patients for each age group.

defined in Table 1. There were 2439 separate identifiable injuries among these 1193 patients (2.04 injuries per patient). Eight thousand nine hundred eighty-eight (66%) patients were men (versus 4718 female patients). Sex was not recorded on 22 patients. The mean age of enrolled patients was 39.4 F 21.5 years (median, 36.3 years; IQR, 23.0 -50.9 years). The mean age of patients with TBI was 42.1 F 24.2 years (median, 39.3 years; IQR, 22.2- 58.5 years). The number of patients chosen to undergo cranial CT scanning varied by age, as shown in Fig. 1. Lowest numbers of CT scanning were noted in the very young (age b 10 years) and the elderly (age N65 years). The number of significant traumatic brain injuries also varied by age (Fig. 2). Most injuries occurred in those patients aged 18 to 24 years. In contrast, the prevalence of significant TBI (number of injuries divided by number of enrollees for each age group) appears to demonstrate a bimodal distribution (Fig. 3). The prevalence was highest among the very young and the very old. Table 2 describes the enrollment and injuries rates for young and old patients. There were 2439 injuries identified in the study population (Table 3). In addition, cranial CT identified 293 cases of shift or mass effect and 48 instances of traumatic brain herniation. Table 3 presents the distribution of specific types of traumatic brain injuries among different age groups, whereas Table 4 presents the distribution of the 342 skull fractures.

Fig. 2

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Most of those with significant TBI were men (843 [71%; 95% CI, 68%-73%]) as compared with women (373 [29%; 95% CI, 27%-32%]). The prevalence of TBI among those chosen to undergo CT scanning was higher in men (9.4%; 95% CI, 8.8%-10.0%) than in women (7.4%; 95% CI, 6.6% -8.2%). Injury patterns varied by race/ethnicity, with 6912 (50%) of enrollees classified as white, 2418 (18%) as black, 1985 (15%) as Hispanic, 330 (2%) as Asian, 158 (1%) as Native American, and 99 (1%) as Middle Eastern, although race/ethnicity was unavailable for 1826 patients. Traumatic brain injury prevalence among CT-scanned patients also varied by race/ethnicity, with the highest prevalence among whites (9.8%; 95% CI, 9.0% -10.4%) and Asians (11.8%; 95% CI, 8.5 -15.8) and lowest prevalence among Native Americans (4.4%; 95% CI, 1.8-8.9%), patients of Middle Eastern decent (4.0%; 95% CI, 1.1% -10.0%), and blacks (6.1%; 95% CI, 5.2% -7.1%).

4. Discussion We assessed the epidemiologic characteristics of patients with blunt head trauma who underwent cranial CT scanning at 21 diverse EDs. The large number and wide range of institutions included in this study make this the first largescale assessment of TBI patterns presenting to emergency medicine centers.

Significant intracranial lesions in patients with trauma (n = 1193) for each age group.

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Fig. 3

Prevalence of significant lesions in patients with trauma for each age group.

It is important to acknowledge, at the outset, that our study represents a selected population, rather than b patients with head trauma.Q We are unable to speculate about patients for whom physicians in the ED chose not to perform cranial CT scanning or about patients with some degree of head trauma who chose not to come to an ED at all. Thus, our estimates of injury prevalence and RR are undoubtedly subject to this (self and physician) selection process. With that proviso in mind, we nevertheless believe the most important finding of this study is the bimodal variation in injury prevalence. Patients with extreme ages (either very young or very old) were more likely to sustain a significant TBI on cranial CT scan as a consequence of blunt trauma. Given that clinicians likely have a lower threshold for the use of radiographic imaging in patients at extremes of age [17,18], and recommendations for liberal use of cranial CT scan in both children and the elderly have been suggested [19,20], the true relative prevalence of injury is likely to be even greater in these groups, in comparison to other patients. The increased risk of injury among these populations has been suggested in previous work [1,13,21-24] and Table 2

Enrollment and injuries among young and old patients

Pediatrics — all patients with blunt trauma

Pediatrics (b 18 y)

Nonpediatrics

No. of pediatric patients No. of patients without traumatic brain injuries No. of patients with traumatic brain injuries Injury prevalence

1669 1493

11 661 10 694

176

967

10.5% (95% CI, 9.1 - 12.1)

8.3% (95% CI, 7.8% - 8.8%)

Geriatrics — all patients with blunt trauma

Geriatrics (N 65 y)

Nongeriatrics

No. of geriatric patients No. of patients without traumatic brain injuries No. of patients with traumatic brain injuries Injury prevalence

2333 (17%) 2040

11 395 (83%) 10 485

293 12.6% (11.2 - 13.9%)

900 7.8% (7.4 - 8.4%)

may be of significant importance in developing decision instruments to identify patients with blunt head injury who require cranial CT scanning [25,26]. Anatomic factors may play a prominent role in the increased risk among pediatric patients. Children have larger head to body ratios that may allow more energy from a traumatic impact to be distributed to their head. In addition, certain mechanisms of injury are unique to children and may increase the risk of TBI. For example, child abuse frequently involves energy directed at the child’s head, and motor vehicle bumpers are in relatively close proximity to the head of pediatric pedestrians. Finally, children are at higher risk for falls, a mechanism of injury associated with an increased risk for TBI [11,27 -29]. The increased risk of TBI in the elderly may be secondary to several factors. Advancing age results in physical disability, cognitive impairment, and cerebral atrophy. Stretching of bridging veins as a consequence of cerebral atrophy may increase the risk of serious TBI associated with even minor blunt trauma [30]. Elderly patients are also more likely to be anticoagulated, which may further increase the risk of TBI after relatively trivial impact [31]. However, a definitive link between anticoagulation and identification of a TBI during ED evaluation has yet to be established [32 -35]. Finally, as with children, the elderly are at increased risk for sustaining a fall, a mechanism frequently associated with traumatic brain injuries [5,6,13,27,36 -40]. Age also appears to play a role in the type of injury a patient sustains. For example, the prevalence of skull fractures decreased with age. Nearly half the children younger than 10 years with significant injuries had a skull fracture, whereas less than 20% of injury victims older than 65 years exhibited this injury. Similarly, intraparenchymal hemorrhages were exceedingly rare in children younger than 10 years. Unlike some prior reports, we did not identify an increased risk of subdural hematoma, compared with other types of brain injury, among elderly patients —there were more subdural hematomas in the elderly, but these were proportional to increases in TBI overall [41]. Epidural hematoma, on the other hand, was much decreased among the elderly subjects in our study. This may be because of

Epidemiology of blunt head injury victims Table 3

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Types of traumatic brain injuries stratified by age

Type of injury

Age b10 y (n = 92)

10 y V Age b 65 y (n = 808)

Skull fracture (n = 342) Epidural hematoma (n = 133) Acute subdural hematoma (n = 376) Extra-axial hematoma (n = 63) Subarachnoid hemorrhage (n = 450) Intraparenchymal hemorrhage (n = 198) Intraventricular hemorrhage (n = 102) Contusion (n = 466) Focal edema (n = 94) Diffuse cerebral edema (n = 72) Diffuse axonal injury (n = 12)

45 (49%; 95% CI, 38% - 60%) 15 (16%; 95% CI, 9% - 24%) 23 (25%; 95% CI, 17% - 35%)

220 (27%; 95% CI, 24% - 30%) 103 (12%; 95% CI, 11% - 15%) 256 (32%; 95% CI, 28% - 35%)

46 (16%; 95% CI, 12% - 20%) 15 (5%; 95% CI, 3% - 8%) 97 (33%; 95% CI, 28% - 39%)

9 (10%; 95% CI, 5% - 18%) 23 (25%; 95% CI, 17% - 35%)

42 (5%; 95% CI, 4% - 7%) 300 (37%; 95% CI, 34% - 41%)

12 (4%; 95% CI, 2% - 7%) 127 (43%; 95% CI, 38% - 49%)

132 (16%; 95% CI, 14% - 19%)

64 (22%; 95% CI, 17% - 27%)

2 (2%; 95% CI, 0% - 8%) 7 (8%; 95% CI, 3% - 15%)

56 (7%; 95% CI, 5% - 9%)

40 (43%; 95% CI, 33% - 54%) 1 (1%; 95% CI, 0% - 6%) 7 (8%; 95% CI, 3% - 15%) 1 (1%; 95% CI, 0% - 6%)

the increased adherence of the dura mater to the skull, which occurs with aging [40]. Among patients undergoing cranial CT imaging, we found that white and Asian ethnicities had the highest prevalence of injury, whereas black ethnicity had the lowest. Prior US population-based studies have found black ethnicity to be associated with a higher incidence of TBI than white ethnicity [13,21]. Although it is possible that differences in access to medical care, mechanisms of injury, and/or variations in physician practice may account for these observations, the meaning of this finding is unclear, and we urge caution regarding the interpretation of this information — which clearly should not be used in any way to determine the need for cranial CT scanning in individual patients. We also observed an increased risk of TBI among male subjects, an observation consistent with multiple prior studies [1,6,13,21,24]. The total number of TBI among men was more than twice the number in women (843 vs 348), which is higher than the 1.6- to 1.9 -fold increase noted in 2 prior population-based studies [13,21]. This does not reflect only a higher number of men chosen for imaging after blunt trauma, as the RR of injury among men was also increased (RR = 1.27) (Table 5). These data once again highlight the public health problem of trauma in the male population. The major limitation to our findings is the obvious potential for selection bias, as discussed above. Nevertheless, with regard to our most important finding — of increased risk of significant injury at extremes of age— this strongly suggests that our raw numbers actually Table 4

327 (40%; 95% CI, 37% - 44%) 69 (9%; 95% CI, 7% - 11%) 57 (7%; 95% CI, 5% - 9%) 7 (1%; 95% CI, 0% - 2%)

Age z 65 y (n = 293)

39 (13%; 95% CI, 10% - 18%) 99 (34%; 95% CI, 28% - 40%) 24 (8%; 95% CI, 5% - 12%) 8 (3%; 95% CI, 1% - 5%) 4 (1%; 95% CI, 0% - 3%)

represent an underestimate of the actual differences in prevalence between these groups and other patients. We did not collect information on mechanism of injury and, thus, can not comment on the risk of TBI when stratified by mechanism of injury. Finally, we identified potential differences in race/ethnicity and the prevalence of TBI on cranial CT scan. These findings may be due to multiple factors, and we are unable to determine the impact each of these factors. Variation in practice patterns (indications for cranial CT scanning) at participating study sites may contribute to the differences identified in race/ ethnicity. Future study is necessary to determine if associations exist between race, medical care provided to those with blunt head trauma, and the presence of TBI. In conclusion, among patients selected for cranial CT scanning after blunt head injury, men, patients younger than 10 years, and those older than 65 years have an increased likelihood of significant TBI. Although this should not be used as a major determinant of the need for cranial CT scanning in individual patients, it can help inform decision making, as well as influence the development of decision instruments for imaging among populations of patients with minor head trauma.

Appendix A. NEXUS study group The following centers and investigators collaborated in this study: Principal investigator: W Mower.

Types of skull fractures stratified by age

Type of injury

Age b 10 y (n = 49)

10 y V Age b 65 y (n = 242)

Age z 65 y (n = 51)

Basilar Complex Depressed Diastasis Linear

3 (6%; 95% CI, 1% - 17%) 6 (12%; 95% CI, 5% - 25%) 13 (27%; 95% CI, 15% - 41%) 6 (12%; 95% CI, 5% - 25%) 21 (43%; 95% CI, 29% - 58%)

26 37 49 12 118

6 (12%; 95% CI, 4% - 24%) 8 (16%; 95% CI, 7% - 29%) 10 (20%; 95% CI, 10% - 33%) 1 (2%; 95% CI, 0% - 10%) 26 (51%; 95% CI, 37% - 65%)

(11%; 95% CI, 7% - 15%) (15%; 95% CI, 11% - 20%) (20%; 95% CI, 15% - 26%) (5%; 95% CI, 3% - 9%) (49%; 95% CI, 42% - 55%)

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Table 5 Relative risk of specific demographic factors for significant TBI Clinical variable

RR

95% CI

Pediatrics (age b 18 y) Age b 10 y Geriatrics (age N 65 y) Male sex

1.23 1.44 1.59 1.27

1.06 -1.44 1.19 -1.77 1.40 -1.80 1.13 -1.43

Co-investigators: J Hoffman and M Herbert. Steering Committee: M Herbert, J Hoffman, W Mower, C Pollack, A Wolfson, and M Zucker. Site investigators: Boston University, Boston Medical Center (Boston, Mass): N Rathlev and G Barest; Case Western Reserve University, Metrohealth System (Cleveland, Ohio): RK Cydulka and B Karaman; Cooper Hospital, University Medical Center (Camden, NJ): C Terregino, A Nyce, and S Ross; Emory University Medical Center (Atlanta, Ga): D Lowery and S Tigges; Hennepin County Medical Center (Minneapolis, Minn): B Mahoney and J Hollerman; Louisiana State University Medical Center, Charity Hospital (New Orleans, La): M Haydel and E Blaudeau; Maricopa Medical Center (Phoenix, Ariz): C Pollack and M Connell; Ohio State University Medical Center (Columbus, Ohio): DR Martin and C Mueller; Stanford University Medical Center (Stanford, Calif): SV Mahadevan and G Arabit; State University of New York at Stonybrook (Stonybrook, NY): P Viccellio and S Fuchs; University of Calgary, Foothills Hospital (Calgary, Canada): G Lazarenko and C Fong; University of California, Davis, Medical Center (Sacramento, Calif): J Holmes and RA McFall; University of California, Irvine (Irvine, Calif): J Krawczyk; University of California, Los Angeles, Center for the Health Sciences (Los Angeles, Calif): J Hoffman and M Zucker; University of California San Diego Medical Center, Hillcrest (San Diego, Calif): D Guss and D Meltzer; University of California, San Francisco at Fresno, University Medical Center (Fresno, Calif): G Hendey and R Lesperance; University of Cincinnati, University Hospital (Cincinnati, Ohio): GJ Fermann and HH Hawkins; University of Missouri, Kansas City, Truman Medical Center (Kansas City, Mo): E Westdorp and S Go; University of Pennsylvania Medical Center (Philadelphia, Pa): J Hollander; University of Pittsburgh Medical Center (Pittsburgh, Pa): A Wolfson and J Towers; Vanderbilt University Medical Center (Nashville, Tenn): V Norton.

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