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

Risk factors, management, and outcomes in isolated parafalcine or tentorial subdural hematomas

INTRODUCTION

Indications for hospitalization in patients with parafalcine or tentorial subdural hematomas (SDH) remain unclear. This study derived and validated a clinical decision rule to identify patients at low risk for complications such that hospitalization can be avoided.

METHODS

A multicenter retrospective medical record review of adult patients with parafalcine or tentorial SDHs was completed. The primary outcome was significant injury, defined as injury that led to neurosurgery, discharge to another facility, or death. A multivariable logistic regression was performed to identify variables independently associated with the outcome in the derivation cohort. These variables were then validated on a separate cohort from a different institution abstracted without knowledge of the identified variables.

RESULTS

In the derivation cohort, 134 patients with parafalcine/tentorial SDHs were identified. The mean age was 63 ± 19 years with 82 (61%) male. Seventy-one (53%) had significant injuries. Variables independently associated with significant injury included: age over 60, adjusted odds ratio (aOR) 3.46 (95% CI 1.24, 9.62), initial Glasgow Coma Scale score below 15, aOR =7.92 (95% CI 2.78, 22.5), and additional traumatic brain injuries (TBIs) on computerized tomography (CT), aOR =5.97 (95% CI 2.48, 14.4). These three variables had a sensitivity of 71/71 (100%, 95% CI 96, 100%) and specificity of 12/63 (19%, 95% CI 10, 31%). The validation cohort (n = 83) had a mean age of 62 ± 22 years with 50 (60%) male. The three variables had a sensitivity of 36/36 (100%, 95% CI 92, 100%) and specificity of 7/47 (15%, 95% CI 6.2, 28%). All 39 (100%, 95% CI 93, 100%) patients from both cohorts who underwent neurosurgery had additional TBI findings on their CT scan.

CONCLUSIONS

Patients with parafalcine/tentorial SDHs who are under 60 years with initial GCS scores of 15 and no addition TBIs on CT are at low risk and may not need hospitalization. Furthermore, patients with isolated parafalcine/tentorial SDHs are unlikely to undergo neurosurgery. Prospective, external validation with a larger sample size is now recommended.

STUDY TYPE

Retrospective Cohort Study.

Isolated subarachnoid hemorrhage in mild traumatic brain injury: is a repeat CT scan necessary? A single-institution retrospective study

BACKGROUND

Traumatic brain injury (TBI) with isolated subarachnoid hemorrhage (iSAH) is a common finding in the emergency department. In many centers, a repeat CT scan is routinely performed 24 to72 h following the trauma to rule out further radiological progression. The aim of this study is to assess the clinical utility of the repeat CT scan in clinical practice.

METHODS

We reviewed the medical charts of all patients who presented to our institution with mild TBI (mTBI) and isolated SAH between January 2015 and October 2017. CT scan at admission and control after 24 to 72 h were examined for each patient in order to detect any possible change. Neurological deterioration, antiplatelet/anticoagulant therapy, coagulopathy, SAH location, associated injuries, and length of stay in hospital were analyzed.

RESULTS

Of the 649 TBI patients, 106 patients met the inclusion criteria. Fifty-four patients were females and 52 were males with a mean age of 68.2 years. Radiological iSAH progression was found in 2 of 106 (1.89) patients, and one of them was under antiplatelet therapy. No neurological deterioration was observed. Ten of 106 (9.4%) patients were under anticoagulation therapy, and 28 of 106 (26.4%) were under antiplatelet therapy.

CONCLUSION

ISAH in mTBI seems to be a radiological stable entity over 72 h with no neurological deterioration. The clinical utility of a repeat head CT in such patients is questionable, considering its radiation exposure and cost. Regardless of anticoagulation/antiplatelet therapy, neurologic observation and symptomatic treatment solely could be a reasonable alternative.

Concurrent Types of Intracranial Hemorrhage are Associated with a Higher Mortality Rate in Adult Patients with Traumatic Subarachnoid Hemorrhage: A Cross-Sectional Retrospective Study

Traumatic subarachnoid hemorrhage (SAH) is the second most frequent intracranial hemorrhage and a common radiologic finding in computed tomography. This study aimed to estimate the risk of mortality in adult trauma patients with traumatic SAH concurrent with other types of intracranial hemorrhage, such as subdural hematoma (SDH), epidural hematoma (EDH), and intracerebral hemorrhage (ICH), compared to the risk in patients with isolated traumatic SAH. We searched our hospital’s trauma database from 1 January, 2009 to 31 December, 2018 to identify hospitalized adult patients ≥20 years old who presented with a trauma abbreviated injury scale (AIS) of ≥3 in the head region. Polytrauma patients with an AIS of ≥3 in any other region of the body were excluded. A total of 1856 patients who had SAH were allocated into four exclusive groups: (Group I) isolated traumatic SAH, n = 788; (Group II) SAH and one diagnosis, n = 509; (Group III) SAH and two diagnoses, n = 493; and (Group IV) SAH and three diagnoses, n = 66. One, two, and three diagnoses indicated occurrences of one, two, or three other types of intracranial hemorrhage (SDH, EDH, or ICH). The adjusted odds ratio with a 95% confidence interval (CI) of the level of mortality was calculated with logistic regression, controlling for sex, age, and pre-existing comorbidities. Patients with isolated traumatic SAH had a lower rate of mortality (1.8%) compared to the other three groups (Group II: 7.9%, Group III: 12.4%, and Group IV: 27.3%, all p < 0.001). When controlling for sex, age, and pre-existing comorbidities, we found that Group II, Group III, and Group IV patients had a 4.0 (95% CI 2.4–6.5), 8.9 (95% CI 4.8–16.5), and 21.1 (95% CI 9.4–47.7) times higher adjusted odds ratio for mortality, respectively, than the patients with isolated traumatic SAH. In this study, we demonstrated that compared to patients with isolated traumatic SAH, traumatic SAH patients with concurrent types of intracranial hemorrhage have a higher adjusted odds ratio for mortality.

Prediction of Mortality in Patients with Isolated Traumatic Subarachnoid Hemorrhage Using a Decision Tree Classifier: A Retrospective Analysis Based on a Trauma Registry System

Background: In contrast to patients with traumatic subarachnoid hemorrhage (tSAH) in the presence of other types of intracranial hemorrhage, the prognosis of patients with isolated tSAH is good. The incidence of mortality in these patients ranges from 0–2.5%. However, few data or predictive models are available for the identification of patients with a high mortality risk. In this study, we aimed to construct a model for mortality prediction using a decision tree (DT) algorithm, along with data obtained from a population-based trauma registry, in a Level 1 trauma center. Methods: Five hundred and forty-five patients with isolated tSAH, including 533 patients who survived and 12 who died, between January 2009 and December 2016, were allocated to training (n = 377) or test (n = 168) sets. Using the data on demographics and injury characteristics, as well as laboratory data of the patients, classification and regression tree (CART) analysis was performed based on the Gini impurity index, using the rpart function in the rpart package in R. Results: In this established DT model, three nodes (head Abbreviated Injury Scale (AIS) score ≤4, creatinine (Cr) <1.4 mg/dL, and age <76 years) were identified as important determinative variables in the prediction of mortality. Of the patients with isolated tSAH, 60% of those with a head AIS >4 died, as did the 57% of those with an AIS score ≤4, but Cr ≥1.4 and age ≥76 years. All patients who did not meet the above-mentioned criteria survived. With all the variables in the model, the DT achieved an accuracy of 97.9% (sensitivity of 90.9% and specificity of 98.1%) and 97.7% (sensitivity of 100% and specificity of 97.7%), for the training set and test set, respectively. Conclusions: The study established a DT model with three nodes (head AIS score ≤4, Cr <1.4, and age <76 years) to predict fatal outcomes in patients with isolated tSAH. The proposed decision-making algorithm may help identify patients with a high risk of mortality.

Neurologic Emergencies in the Elderly

Neurologic diseases are a major cause of death and disability in elderly patients. Due to the physiologic changes and increased comorbidities that occur as people age, neurologic diseases are more common in geriatric patients and a major cause of death and disability in this population. This article discusses the elderly patient presenting to the emergency department with acute ischemic stroke, transient ischemic attack, intracerebral hemorrhage, subarachnoid hemorrhage, chronic subdural hematoma, traumatic brain injury, seizures, and central nervous system infections. This article reviews the subtle presentations, difficult workups, and complicated treatment decisions as they pertain to our older patients."

Practical one-dimensional measurements of age-related brain atrophy are validated by 3-dimensional values and clinical outcomes: a retrospective study

Background

Age-related brain atrophy has been represented by simple 1-dimensional (1-D) measurements on computed tomography (CT) for several decades and, more recently, with 3-dimensional (3-D) analysis, using brain volume (BV) and cerebrospinal fluid volume (CSFV). We aimed to show that simple 1-D measurements would be associated with 3-D values of age-related atrophy and that they would be related to post-traumatic intracranial hemorrhage (ICH).

Methods

Patients ≥60 years with head trauma were classified with central atrophy (lateral ventricular body width >30 mm) and/or cortical atrophy (sulcus width ≥2.5 mm). Composite atrophy was the presence of central or cortical atrophy. BV and CSFV were computed using a Siemens Syngo workstation (VE60A).

Results

Of 177 patients, traits were age 78.3 ± 10, ICH 32.2 %, central atrophy 39.5 %, cortical atrophy 31.1 %, composite atrophy 49.2 %, BV 1,156 ± 198 mL, and CSFV 102.5 ± 63 mL. CSFV was greater with central atrophy (134.4 mL), than without (81.7 mL, p < 0.001). BV was lower with cortical atrophy (1,034 mL), than without (1,211 mL; p < 0.001). BV was lower with composite atrophy (1,103 mL), than without (1,208 mL; p < 0.001). CSFV was greater with composite atrophy (129.1 mL), than without (76.8 mL, p < 0.001). CSFV÷BV was greater with composite atrophy (12.3 %), than without (6.7 %, p < 0.001). Age was greater with composite atrophy (80.4 years), than without (76.3, p = 0.006). Age had an inverse correlation with BV (p < 0.001) and a direct correlation with CSFV (p = 0.0002) and CSFV÷BV (p < 0.001). ICH was greater with composite atrophy (49.4 %), than without (15.6 %; p < 0.001; odds ratio = 5.3). BV was lower with ICH (1,089 mL), than without (1,188 mL; p = 0.002). CSFV÷BV was greater with ICH (11.1 %), than without (8.7 %, p = 0.02). ICH was independently associated with central atrophy (p = 0.001) and cortical atrophy (p = 0.003).

Conclusions

Simple 1-D measurements of age-related brain atrophy are associated with 3-D values. Clinical validity of these methods is also supported by their association with post-injury ICH. Intracranial 3-D software is not available on many CT scanners and can be cumbersome, when available. Simple 1-D measurements, using the study methodology, are a practical method to objectify the presence of age-related brain atrophy.

Risk factors for delayed neuro-surgical intervention in patients with acute mild traumatic brain injury and intracranial hemorrhage

Background

Mild traumatic brain injury (TBI) patients with initial traumatic intracranial hemorrhage (tICH) and without immediate neuro-surgical intervention require close monitoring of their neurologic status. Progressive hemorrhage and neurologic deterioration may need delayed neuro-surgical intervention. This study aimed to determine the potential risk factors of delayed neuro-surgical intervention in mild TBI patients with tICH on admission.

Methods

Three hundred and forty patients with mild TBI and tICH who did not need immediate neuro-surgical intervention on admission were evaluated retrospectively. Their demographic information, clinical evaluation, laboratory data, and brain CT was reviewed. Delayed neuro-surgical intervention was defined as failure of non-operative management after initial evaluation. Risk factors of delayed neuro-surgical intervention on admission were analyzed.

Results

Delayed neuro-surgical intervention in mild TBI with tICH on initial brain CT accounted for 3.8 % (13/340) of all episodes. Higher WBC concentration, higher initial ISS, epidural hemorrhage (EDH), higher volume of EDH, midline shift, and skull fracture were risk factors of delayed neuro-surgical intervention. The volume of EDH and skull fracture is independent risk factors. One cubic centimeter (cm3) increase in EDH on initial brain CT increased the risk of delayed neurosurgical intervention by 16 % (p = 0.011; OR: 1.190, 95 % CI:1.041–1.362).

Conclusions

Mild TBI patients with larger volume of EDH have higher risk of delayed neuro-surgical interventions after neurosurgeon assessment. Longer and closer neurological function monitor and repeated brain image is required for those patients had initial larger EDH. A large-scale, multi-centric trial with a bigger study population should be performed to validate the findings.

Recommendations for the evaluation and management of observation services: a consensus white paper: the Society of Cardiovascular Patient Care

Observation Services (OS) was founded by emergency physicians in an attempt to manage "boarding" issues faced by emergency departments throughout the United States. As a result, OS have proven to be an effective strategy in reducing costs and decreasing lengths of stay while improving patient outcomes. When OS are appropriately leveraged for maximum efficiency, patients presenting to emergency departments with common disease processes can be effectively treated in a timely manner. A well-structured observation program will help hospitals reduce the number of inappropriate, costly inpatient admissions while avoiding the potential of inappropriate discharges. Observation medicine is a complicated multidimensional issue that has generated much confusion. This service is designed to provide the best possible patient care in a value-based purchasing environment where quality, cost, and patient satisfaction must continually be addressed. Observation medicine is a service not a status. Therefore, patients are admitted to the service as outpatients no matter whether they are placed in a virtual or dedicated observation unit. The key to a successful observation program is to determine how to maximize efficiencies. This white paper provides the reader with the foundational guidance for observational services. It defines how to set up an observational service program, which diagnoses are most appropriate for admission, and what the future holds. The goal is to help care providers from any hospital deliver the most appropriate level of treatment, to the most appropriate patient, in the most appropriate location while controlling costs.

Traumatic intracranial hemorrhage correlates with preinjury brain atrophy, but not with antithrombotic agent use: a retrospective study

BACKGROUND

The impact of antithrombotic agents (warfarin, clopidogrel, ASA) on traumatic brain injury outcomes is highly controversial. Although cerebral atrophy is speculated as a risk for acute intracranial hemorrhage, there is no objective literature evidence.

MATERIALS AND METHODS

This is a retrospective, consecutive investigation of patients with signs of external head trauma and age ≥60 years. Outcomes were correlated with antithrombotic-agent status, coagulation test results, admission neurologic function, and CT-based cerebral atrophy dimensions.

RESULTS

Of 198 consecutive patients, 36% were antithrombotic-negative and 64% antithrombotic-positive. ASA patients had higher arachidonic acid inhibition (p = 0.04) and warfarin patients had higher INR (p<0.001), compared to antithrombotic-negative patients. Antithrombotic-positive intracranial hemorrhage rate (38.9%) was similar to the antithrombotic-negative rate (31.9%; p = 0.3285). Coagulopathy was not present on the ten standard coagulation, thromboelastography, and platelet mapping tests with intracranial hemorrhage and results were similar to those without hemorrhage (p≥0.1354). Hemorrhagic-neurologic complication (intracranial hemorrhage progression, need for craniotomy, neurologic deterioration, or death) rates were similar for antithrombotic-negative (6.9%) and antithrombotic-positive (8.7%; p = 0.6574) patients. The hemorrhagic-neurologic complication rate was increased when admission major neurologic dysfunction was present (63.2% versus 2.2%; RR = 28.3; p<0.001). Age correlated inversely with brain parenchymal width (p<0.001) and positively with lateral ventricular width (p = 0.047) and cortical atrophy (p<0.001). Intracranial hemorrhage correlated with cortical atrophy (p<0.001) and ventricular width (p<0.001).

CONCLUSIONS

Intracranial hemorrhage is not associated with antithrombotic agent use. Intracranial hemorrhage patients have no demonstrable coagulopathy. The association of preinjury brain atrophy with acute intracranial hemorrhage is a novel finding. Contrary to antithrombotic agent status, admission neurologic abnormality is a predictor of adverse post-admission outcomes. Study findings indicate that effective hemostasis is maintained with antithrombotic therapy.

Comprehensive assessment of isolated traumatic subarachnoid hemorrhage

Recent studies have shown that isolated traumatic subarachnoid hemorrhage (tSAH) in the setting of a high Glasgow Coma Scale (GCS) score (13-15) is a relatively less severe finding not likely to require operative neurosurgical intervention. This study sought to provide a more comprehensive assessment of isolated tSAH among patients with any GCS score, and to expand the analysis to examine the potential need for aggressive medical, endovascular, or open surgical interventions in these patients. By undertaking a retrospective review of all patients admitted to our trauma center from 2003-2012, we identified 661 patients with isolated tSAH. Only four patients (0.61%) underwent any sort of aggressive neurosurgical, medical, or endovascular intervention, regardless of GCS score. Most tSAH patients without additional systemic injury were discharged home (68%), including 53% of patients with a GCS score of 3-8. However, older patients were more likely to be discharged to a rehabilitation facility (p<0.01). There were six (1.7%) in-hospital deaths, and five patients of these patients were older than 80 years old. We conclude that isolated tSAH, regardless of admission GCS score, is a less severe intracranial injury that is highly unlikely to require aggressive operative, medical, or endovascular intervention, and is unlikely to be associated with major neurologic morbidity or mortality, except perhaps in elderly patients. Based upon our findings, we argue that impaired consciousness in the setting of isolated tSAH should strongly compel a consideration of non-traumatic factors in the etiology of the altered neurological status.

Peroxisome proliferator-activated receptors: "key" regulators of neuroinflammation after traumatic brain injury

Traumatic brain injury is characterized by neuroinflammatory pathological sequelae which contribute to brain edema and delayed neuronal cell death. Until present, no specific pharmacological compound has been found, which attenuates these pathophysiological events and improves the outcome after head injury. Recent experimental studies suggest that targeting peroxisome proliferator-activated receptors (PPARs) may represent a new anti-inflammatory therapeutic concept for traumatic brain injury. PPARs are “key” transcription factors which inhibit NFκB activity and downstream transcription products, such as proinflammatory and proapoptotic cytokines. The present review outlines our current understanding of PPAR-mediated neuroprotective mechanisms in the injured brain and discusses potential future anti-inflammatory strategies for head-injured patients, with an emphasis on the putative beneficial combination therapy of synthetic cannabinoids (e.g., dexanabinol) with PPARα agonists (e.g., fenofibrate).

Do children with blunt head trauma and normal cranial computed tomography scan results require hospitalization for neurologic observation?

STUDY OBJECTIVE

Children evaluated in the emergency department (ED) with minor blunt head trauma, defined by initial Glasgow Coma Scale (GCS) scores of 14 or 15, are frequently hospitalized despite normal cranial computed tomography (CT) scan results. We seek to identify the frequency of neurologic complications in children with minor blunt head trauma and normal ED CT scan results.

METHODS

We conducted a prospective, multicenter observational cohort study of children younger than 18 years with blunt head trauma (including isolated head or multisystem trauma) at 25 centers between 2004 and 2006. In this substudy, we analyzed individuals with initial GCS scores of 14 or 15 who had normal cranial CT scan results during ED evaluation. An abnormal imaging study result was defined by any intracranial hemorrhage, cerebral edema, pneumocephalus, or any skull fracture. Patients with normal CT scan results who were hospitalized were followed to determine neurologic outcomes; those discharged to home from the ED received telephone/mail follow-up to assess for subsequent neuroimaging, neurologic complications, or neurosurgical intervention.

RESULTS

Children (13,543) with GCS scores of 14 or 15 and normal ED CT scan results were enrolled, including 12,584 (93%) with GCS scores of 15 and 959 (7%) with GCS scores of 14. Of 13,543 patients, 2,485 (18%) were hospitalized, including 2,107 of 12,584 (17%) with GCS scores of 15 and 378 of 959 (39%) with GCS scores of 14. Of the 11,058 patients discharged home from the ED, successful telephone/mail follow-up was completed for 8,756 (79%), and medical record, continuous quality improvement, and morgue review was performed for the remaining patients. One hundred ninety-seven (2%) children received subsequent CT or magnetic resonance imaging (MRI); 5 (0.05%) had abnormal CT/MRI scan results and none (0%; 95% confidence interval [CI] 0% to 0.03%) received a neurosurgical intervention. Of the 2,485 hospitalized patients, 137 (6%) received subsequent CT or MRI; 16 (0.6%) had abnormal CT/MRI scan results and none (0%; 95% CI 0% to 0.2%) received a neurosurgical intervention. The negative predictive value for neurosurgical intervention for a child with an initial GCS score of 14 or 15 and a normal CT scan result was 100% (95% CI 99.97% to 100%).

CONCLUSION

Children with blunt head trauma and initial ED GCS scores of 14 or 15 and normal cranial CT scan results are at very low risk for subsequent traumatic findings on neuroimaging and extremely low risk of needing neurosurgical intervention. Hospitalization of children with minor head trauma after normal CT scan results for neurologic observation is generally unnecessary.

The changing face of mild head injury: temporal trends and patterns in adolescents and adults from 1997 to 2008

OBJECTIVE

To explore the temporal trend of incidence, causes of injury and main characteristics of adolescent and adult subjects with mild head injury (MHI).

DESIGN

This study had a retrospective design.

SETTING

The study was conducted in a longitudinal database of an Italian Emergency Department (ED).

PARTICIPANTS

The study comprised 19124 consecutive subjects who visited and were managed within 24 h from the event, according to a predefined protocol for MHI from 1997 to 2008.

MAIN OUTCOME MEASURES

Incidence, demography, cause of injury and characteristics of any post-traumatic intracranial lesion within 7 days from MHI.

RESULTS

The number of subjects with MHI decreased from 2019 per year (1997-1999) to 1232 per year (2006-2008; P for linear trend <0.001), without differences in the total number of subjects visited in the ED. The decrease was observed in all age-decades, in particular, in subjects in the age ranges of 20-29 and 30-39 years. Over time, the age of subjects with MHI lost a bimodal distribution, and the mean age increased from 43 (25-69) years (median (interquartile range)) in 1997-1999 to 56 (33-78) years in 2006-2008 (P<0.001). The prevalence of falls increased from 36.5% to 55.0%, whereas crashes fell from 53.2% to 31.9%. The incidence of subdural haematoma (SDH) and epidural haematoma (EDH) did not change over time, whereas traumatic subarachnoid haemorrhage (t-SAH) and intra-cerebral haematoma/brain contusion (ICH) increased (from 0.7% to 1.9% and from 2.5% to 3.2%; P for trend: <0.001 for both.

CONCLUSIONS

The incidence and the clinical characteristics of MHI subjects are rapidly changing in our setting. These data need to be considered in defining the effectiveness of preventive measures and deciding resource allocation.

Prediction of intracranial computed tomography findings in patients with minor head injury by using logistic regression

Object

The aim of this study was to develop a decision rule for physicians in developing countries to identify patients with minor head injury who will benefit from emergency brain CT scanning.

Methods

Three hundred eighteen patients with a history of blunt head trauma and a Glasgow Coma Scale (GCS) score ≥ 13 who had presented within 12 hours of trauma underwent nonenhanced brain CT and were included in this prospective study. Computed tomography findings that necessitated neurosurgical care (either observation or intervention) were considered as positive findings. Logistic regression was used to develop the decision rule.

Results

Computed tomography scans were always normal in patients < 65 years old who did not have an obvious head wound, a raccoon sign, vomiting, memory deficit, or a decrease in their GCS score. Patients with 1 major criterion (GCS score < 14, raccoon sign, failure to remember the impact, age > 65 years, or vomiting) or 2 minor criteria (wound at the scalp or GCS score < 15) had an abnormal CT scan in 13% of the cases.

Conclusions

The decision rule developed by the authors appears to be 100% sensitive and 46% specific for positive findings on brain CT and will, in developing countries, help clarify the decision to obtain scans.

Clinical policy: neuroimaging and decisionmaking in adult mild traumatic brain injury in the acute setting

This clinical policy provides evidence-based recommendations on select issues in the management of adult patients with mild traumatic brain injury (TBI) in the acute setting. It is the result of joint efforts between the American College of Emergency Physicians and the Centers for Disease Control and Prevention and was developed by a multidisciplinary panel. The critical questions addressed in this clinical policy are: (1) Which patients with mild TBI should have a noncontrast head computed tomography (CT) scan in the emergency department (ED)? (2) Is there a role for head magnetic resonance imaging over noncontrast CT in the ED evaluation of a patient with acute mild TBI? (3) In patients with mild TBI, are brain specific serum biomarkers predictive of an acute traumatic intracranial injury? (4) Can a patient with an isolated mild TBI and a normal neurologic evaluation result be safely discharged from the ED if a noncontrast head CT scan shows no evidence of intracranial injury? Inclusion criteria for application of this clinical policy's recommendations are nonpenetrating trauma to the head, presentation to the ED within 24 hours of injury, a Glasgow Coma Scale score of 14 or 15 on initial evaluation in the ED, and aged 16 years or greater. The primary outcome measure for questions 1, 2, and 3 is the presence of an acute intracranial injury on noncontrast head CT scan; the primary outcome measure for question 4 is the occurrence of neurologic deterioration.