Clinical Policy: Neuroimaging and Decisionmaking in Adult Mild Traumatic Brain Injury in the Acute Setting

Abstract

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.

Introduction

There are more than 1 million emergency department (ED) visits annually for traumatic brain injury (TBI) in the United States.1, 2 The majority of these visits are for “mild” injuries that are primarily the result of falls and motor vehicle crashes.1, 2 In nonpediatric patients, the highest incidence of mild TBI is seen in males between the ages of 15 and 24 years and in men and women 65 years of age and older.³ It has been reported that up to 15% of patients with head trauma evaluated in the ED with a Glasgow Coma Scale (GCS) score of 15 will have an acute lesion on head computed tomography (CT); less than 1% of these patients will have a lesion requiring a neurosurgical intervention.4, 5, 6, 7, 8, 9 Depending on how disability is defined, 5% to 15% of patients with mild TBI may have compromised function 1 year after their injury.10, 11

The challenge to the emergency physician is identifying which patients with a head injury have an acute traumatic intracranial injury,^⁎ and which patients can be safely sent home. The initial version of this clinical policy was published in 2002 and designed to provide the best evidence available to answer these questions.¹² Since then, several well-designed studies have been published that have added to our understanding of mild TBI and assist in clinical decisionmaking.5, 6, 8, 9, 13 Consequently, this clinical policy provides an update of the 2002 document.

The question of how best to define a mild TBI is of great importance and has been a source of confusion.¹⁴ A small subset of these patients will harbor a life-threatening injury; some will have neurocognitive sequelae for days to months after the injury.15, 16 In fact, it is difficult to convince a patient disabled from the postconcussive syndrome that their injury was “mild.” Unfortunately, there exists no consensus regarding classification. Terms used have included “concussion,” “mild TBI,” “minor TBI,” “minimal TBI,” “grade I TBI,” “class I TBI,” and “low- risk TBI.” Even the terms “head” and “brain” have been used interchangeably. Head injury and TBI are 2 distinct entities that are often, but not necessarily, related. A head injury is best defined as an injury that is clinically evident on physical examination and is recognized by the presence of ecchymoses, lacerations, deformities, or cerebrospinal fluid leakage. A traumatic brain injury refers specifically to an injury to the brain itself and is not always clinically evident; if unrecognized, it may result in an adverse outcome.

The American Congress of Rehabilitation Medicine delineated inclusion criteria for a diagnosis of mild TBI, of which at least 1 of the following must be met¹⁷:

• Any period of loss of consciousness of less than 30 minutes and GCS score of 13 to 15 after this period of loss of consciousness;

• Any loss of memory of the event immediately before or after the accident, with posttraumatic amnesia of less than 24 hours; or

• Any alteration in mental state at the time of the accident (eg, feeling dazed, disoriented, or confused).

The Centers for Disease Control and Prevention has developed a similar conceptual definition for mild TBI¹⁸: Occurrence of injury to the head, resulting from blunt trauma or acceleration or deceleration forces, with one or more of the following conditions attributable to the head injury during the surveillance period:

• Any period of observed or self-reported transient confusion, disorientation, or impaired consciousness

• Any period of observed or self-reported dysfunction of memory (amnesia) around the time of injury

• Observed signs of other neurologic or neuropsychological dysfunction

• Any period of observed or self-reported loss of consciousness lasting 30 minutes or less.

Both definitions are broad and contribute to the difficulty of interpreting the mild TBI literature.

Historically, the system most often used for grading severity of brain injury is the GCS. The phrase “mild TBI” is usually applied to patients with a score of 13 or greater. Some authors have suggested that patients with a GCS score of 13 be excluded from the “mild” category and placed into the “moderate” risk group because of their high incidence of lesions requiring neurosurgical intervention.19, 20, 21 Lesions requiring neurosurgical intervention may not be the only injuries that require identification. In a prospective study, patients with a GCS score of 13 or greater were grouped according to the presence or absence of acute intracranial injury.²⁰ Despite having GCS scores of 13 to 15, those patients with intraparenchymal lesions performed on neuropsychological testing similar to those patients categorized as having moderate TBI (GCS scores 9 to 12).

Created by Teasdale and Jennett²² in 1974, the GCS was developed as a standardized clinical scale to facilitate reliable interobserver neurologic assessments of comatose patients with head injury. The original studies applying the GCS score as a tool for assessing outcome required that coma be present for at least 6 hours.22, 23, 24 The scale was not designed to diagnose patients with mild or even moderate TBI, nor was it intended to supplant a neurologic examination. Instead, the GCS was designed to provide an easy-to-use assessment tool for serial evaluations by relatively inexperienced care providers and to facilitate communication between care providers on rotating shifts.²² This need was especially great because CT scanning was not yet available. Since its introduction, the GCS has become quite useful for diagnosing severe and moderate TBI and for prioritizing interventions in these patients. Nevertheless, for mild TBI, a single GCS score is of limited prognostic value and is insufficient to determine the degree of parenchymal injury after trauma.²² On the other hand, serial GCS scores are quite valuable in patients with mild TBI. A low GCS score that remains low or a high GCS score that decreases predicts a poorer outcome than a high GCS score that remains high or a low GCS score that progressively improves.24, 25 From an emergency medical services’ and ED perspective, the key to using the GCS in patients with mild TBI is in serial determinations. When head CT is not available, serial GCS scores clearly are the best method for detecting patients who require a neurosurgical procedure. The GCS score continues to play this role and to provide important prognostic information. However, the previous discussion makes it clear that the use of a single GCS determination cannot be used solely in diagnosing mild TBI. In one of the original multicenter studies validating the scale in the pre-CT era, approximately 13% of patients who became comatose had an initial GCS of 15.²⁴

The immediate challenge in the ED lies in identifying the apparently well, neurologically intact patient who has a potentially significant intracranial injury. These patients are the focus of this clinical policy. A second challenge is to identify those patients at risk for having prolonged postconcussive symptoms and those at risk for the postconcussive syndrome in order to ensure proper discharge planning. Meeting the second challenge has proven to be elusive and remains an area in need of research.

Increased attention has been brought to bear on concussions and postconcussive issues as a result of the wars in Afghanistan and Iraq. TBI has been labeled the “signature injury” resulting from these conflicts. The proportion of military personnel presenting with a blunt TBI has increased dramatically, primarily because of an increase in survival after exposure to concussive weapons (primarily a result of lower-yield improvised explosive devices, coupled with modern body armor that reduces fatal penetrating injuries). In the Afghanistan/Iraq conflicts, approximately 20% of returning combat personnel have experienced a TBI in theater.²⁶