Chapter 3 - Mild traumatic brain injury and concussion: terminology and classification

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Abstract

Traumatic brain injury (TBI) is a major cause of morbidity and mortality throughout the world. Mild TBI, which is typically defined by Glasgow Coma Scale score ≥ 13, accounts for the vast majority of all TBIs, particularly in the setting of sports-related injuries. The terms concussion and TBI are often used interchangeably, both in the medical literature and in clinical care of this patient population. However, the lack of clearly defined definitions of these terms often leads to confusion, and this confusion may lead to delayed diagnosis and inconsistent management of affected patients. Here, we review the current terminology and classification of mild TBI and concussion. We will also discuss recent efforts to stratify these injuries into clinically relevant subtypes or profiles that are both diagnostic- and treatment-targeted.

Introduction

Traumatic brain injury (TBI) is a major cause of morbidity and mortality throughout the world. Globally, there are an estimated 10 million deaths or hospitalizations annually due to TBI (Langlois et al., 2006b). In the United States alone, there are approximately 1.4 million emergency department visits, hospitalizations, or deaths due to TBI, and this figure likely does not account for the vast majority of mild TBIs, which often do not receive medical attention (Langlois et al., 2006a).

Mild TBI (mTBI) accounts for 58–88% of all TBIs, according to epidemiologic studies (Bruns and Hauser, 2003). In fact, some sources estimate as many as 3.8 million sports-related TBIs occur each year in the United States alone. Potential reasons for the lack of clarity in reported incidence include the heterogeneous nature of mTBI, and the lack of a standardized definition for this condition. The terms concussion and mTBI are often used interchangeably in both clinical and research settings. Nonetheless, there remains no consensus regarding the precise definition of either term. Clinically, this has significant implications in both the diagnosis and treatment of affected patients. From a research perspective, variations in diagnostic criteria result in heterogeneous patient populations that confound trial outcomes, and this may be one reason for the many failed clinical trials testing TBI treatments.

Recent efforts have focused on refining the definition of mTBI and concussion, and identifying disease subtypes to better stratify these patients and thereby individualize treatment regimens and optimize clinical trials. In this chapter, we will review the current terminology and classification of mTBI and concussion.

Section snippets

Definition of mild traumatic brain injury and concussion

The terms mTBI and concussion are often used interchangeably in the trauma literature and the clinical vernacular. The Veterans Affairs and Department of Defense (VA/DoD) clinical practice guideline on the management of concussion/mTBI indicates that the term “concussion” may be preferable when communicating with patients and caregivers, since it suggests a transient condition and avoids the stigma associated with the terms “brain damage” or “brain injury” (Management of Concussion/mTBI Working

Concussion subtype classification

Historically, concussion has been treated as a homogeneous entity. As alluded to previously, this has implications for clinical management and for research efforts focused on this patient population. In the clinical setting, the diagnosis of concussion is frequently made without further specification of the specific signs and symptoms. Conventional treatment options for concussion have been limited, and physical and cognitive rest are often prescribed uniformly without further consideration of

Conclusions

Recent scientific investigations have greatly enhanced our understanding of the neurophysiologic consequences of traumatic head injuries. Nevertheless, clinical management of patients with TBI remains a challenge, at least in part due to the lack of clear diagnostic criteria for mTBI and concussion. Neurotrauma investigators must therefore focus on clearly delineating the clinical, radiographic, and laboratory features of concussion. In effect, efforts must focus on changing concussion from a

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