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INTRODUCTION

Traumatic brain injury (TBI) is an exemplar of the advantages of a neuropsychiatric approach to the diagnosis and treatment of neurobehavioral disorders. The forces that act on the brain to cause neurotrauma typically result in a profile of regional brain damage that maps nicely onto the neuropsychiatric sequelae and functional distress commonly encountered by survivors of such injury. In turn, the effects of living with these neurobehavioral sequelae, including the meaning and the significance of being identified as “brain injured,” influence the quality of life of the individual and their caregivers. Failure to appreciate these complex but predictable relationships impedes the proper assessment and treatment of the individual with a TBI. This chapter reviews the current knowledge of the neurobiological effects of TBI, with special emphasis on how these processes inform the understanding of the clinical presentation and treatment of a person with neurobehavioral complications of neurotrauma.

CLASSIFICATION AND EPIDEMIOLOGY

TBI is typically defined as a change in brain function occurring in response to an external force applied to the head.1 Each year in the United States, approximately 3 million Americans sustain a TBI, with nearly 300,000 hospitalized and 56,000 dying on account of their injuries.2 Two major risk factors associated with TBI include male gender and age in the following three brackets, >75 years, 15–24 years, and 0–4 years. The most common mechanisms of injury include falls, followed by motor vehicle accidents, being struck by or against an object, and violence.2

TBI severity is typically classified as mild, moderate, or severe based on the duration of loss of consciousness (LOC), post-traumatic amnesia (PTA)—defined as the time point at which individual becomes oriented and can once again form and recall new memories, and the highest Glasgow Coma Scale (GCS) within the first 24 hours after injury.3,4 Table 30-1 uses these parameters to summarize the classification scheme for TBI.

TABLE 30-1Parameters of TBI Injury Severity.

Severe TBI is defined by LOC > 24 hours, GCS 3–8, and PTA >1 week. Moderate TBI is defined by LOC >30 min and <24 hours, GCS 9–12, and PTA lasting 24 hours–1 week. Cognitive, behavioral, and motor symptoms resulting from TBI tend to increase with increasing injury severity. Moderate-to-severe injuries are typically accompanied by focal and/or diffuse brain lesions that can be visualized on computed tomography (CT) or magnetic resonance imaging (MRI). Among a cohort of individuals hospitalized at acute care facilities after ...

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