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  • Updated 07.26.2019
  • Released 10.01.1988
  • Expires For CME 07.26.2022

Minor closed head injury

Introduction

This article includes discussion of minor closed head injury, minor head injury, and mild traumatic brain injury. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Mild traumatic brain injury has quickly become one of the most recognized and publicized neurologic disorders. Preliminary evidence suggests that athletes who experience sports-related concussion may be at risk for developing pathological brain changes, and the National Football League (NFL) has come under increased scrutiny in their handling of athletes with mild traumatic brain injury. This has resulted in numerous rule changes and changes to the way players are handled on and off the field. Sports concussion awareness is a major focus of the National College Athletic Association (NCAA) and other amateur organizations, with all 50 states now having passed legislation to protect young athletes from permanent brain injury. Blast-related mild traumatic brain injury has become the signature injury of the Iraq and Afghanistan conflicts, and our wounded warriors are now starting to find their way into mainstream clinical practice. The author provides a comprehensive review of mild traumatic brain injury and highlights current insights into the epidemiology, mechanism (blast, falls, and sports), and physiology of mild traumatic brain injury. He goes on to provide a review of the latest neuroimaging techniques and chronic traumatic encephalopathy, finishing with a detailed discussion on the management of associated symptoms.

Key points

• Mild traumatic brain injury is arguably 1 of the most highly publicized neurologic disorders.

• The field is rapidly evolving despite a lack of evidence-based research and funding for such studies.

• Preliminary evidence suggests that repeated concussions can lead to pathological brain abnormalities that resemble those of Alzheimer disease and/or other neurodegenerative disorders.

• There is currently no objective test to measure mild traumatic brain injury.

• Most concussions resolve spontaneously within 10 to 14 days.

Historical note and terminology

From the time of Hippocrates, theories of cerebral concussion have been used as bases for medical care of patients with minor closed head injury. Hippocrates himself introduced the concept of commotio cerebri, unconsciousness due to mechanical agitation of the brain. During medieval times an alternative theory implicated skull fracture and was popular. Ambrose Pare and subsequent French authorities reemphasized the importance of reversible, diffuse cerebral dysfunction resulting from mechanical agitation. By the 18th century, the entity of cerebral concussion was well known to clinicians, and many hypotheses addressed pathogenesis (25). Insight into cerebral acceleration as the cause of concussion was provided by the work of a number of early and more recent investigators (119; 286).

The mechanism by which this cerebral commotion came about remained elusive. Stromeyer hypothesized impaired cerebral blood flow, his "anemic" theory of concussion (337). However, experimental concussion was soon produced in a cardiectomized animal (371). Koch and Filene demonstrated that repeated minor experimental head injuries can be cumulative and can result in severe and even fatal damage (186). Their results were supported by Denny-Brown and Russell, and the "double impact" syndrome became a popular explanation for sports-related deaths (85). Throughout the 19th century, investigators such as Petit, Bell, and Cooper advanced clinical knowledge, especially in distinguishing benign traumatic loss of consciousness from the coma associated with severe head injury and intracranial hematomas. Investigators now tend to prefer the term “traumatic brain injury” to that of “head injury.”

The recognition of persistent neurobehavioral problems that follow apparently minor head injury (postconcussion syndrome) was late in coming and remains incompletely understood. As recently as 1936, Penfield believed that postconcussion syndrome resulted from arachnoid adhesions and recommended therapeutic pneumoencephalography (276).

Classification and understanding of minor head injury has been impeded by a lack of standard nomenclature. Terms such as "mild," "minor," "moderate," "minimal," and "trivial" are applied to head injuries without precise or universal definitions. This lack makes comparisons among patient populations difficult and interferes with the development of therapeutic guidelines. The introduction of the Glasgow Coma Scale was an important step in standardizing minor head injury nomenclature (341). Groundbreaking studies such as those of Klauber and associates used the Glasgow Coma Scale score to define head injury categories (184). Over the years, a simple scale, based on the Glasgow Coma Scale, has been used to distinguish "moderate" from "mild" closed head injury. This traditional classification assigns all patients with Glasgow Coma Scale scores of 13 or above to the mild category; patients whose scores are 9 to 12 are considered moderate (96). That this system is somewhat arbitrary cannot be denied. Not only is it not obvious where the division between mild and moderate should be, it is not even clear what severity is being measured. Two particular problems are the severity of injury in patients whose Glasgow Coma Scale scores are 13 and the wide range of severity in patients with scores of 15. The incidence of traumatic intracranial hematomas and other intracranial lesions is as high in patients who present with Glasgow Coma Scale scores of 13 as it is with scores of 9 to 12 (332; 357). A large range of patients are represented by Glasgow Coma Scale scores of 15, from the most trivial injury and normal neurologic examination to the impaired arousability and memory that complicate serious concussion or developing hematoma (331). This author introduced the Head Injury Severity Scale to address some of these issues (333). In the 1990s, IMPACT was introduced and the NFL formed its mild traumatic brain injury committee. (227). There was little attention given to concussion until the mid 2000s with the release of the chronic traumatic encephalopathy data; prior to that, the focus was to rule out catastrophic brain injury.

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