Management of Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is ubiquitous and is increasingly being recognized in both the media and diverse clinical practices because of significant prevalence and morbidity. It is estimated that approximately 5.3 million people in the US have TBI-related disability.1 In the US, up to 1.7 million people sustain a TBI every year, of which 1.4 million are treated in emergency departments, yielding 275,000 hospitalizations and 52,000 fatalities, with an overall cost of $76.5 billion.2 Males are at increased risk for sustaining TBIs.3,4

More than 70% of the cases of TBI are mild (mTBI), which makes this subgroup of particular clinical interest. The cost of managing mTBI in the first year ($4600) is much less than that for managing moderate or severe TBI ($36,000), but because the vast majority of brain injury cases are mild, they are the main contributor to cumulative costs.

Many clinicians are uncomfortable with the diagnosis and management of mTBIprobably because of the lack of validated and standardized treatments as well as a poor understanding of the natural history of TBI. Considerable overlap exists between TBI and disorders in cognition, behavior, and personality, which can provide even greater clinical challenges for health care professionals.

This review on mTBI focuses on the clinical and pathophysiologic features of this disease process and on current treatment guidelines and prognosis.

Understanding TBIs

Brain trauma categorization takes into consideration injury severity, pathoanatomic damage, physical mechanism, and pathophysiology. Traditional schemes for diagnosis and grading of TBI severity have incorporated some combination of Glasgow Coma Scale (GCS) score, posttraumatic amnesia duration, duration of loss of consciousness, and presence of other clinical symptoms following a head injury. However, a universally accepted definition of mTBI has proved elusive. A recently published review of mTBI literature revealed approximately 40 different definitions used by various authors and organization.5 The issue is clouded further by the use of the term concussion, which is sometimes used synonymously with mTBI but at other times is considered a specific subset of mTBI.

In this review, we avoid the use of the term concussion and discuss mTBI as defined by DSM-5: initial GCS score of 13 to 15, posttraumatic amnesia of less than 24 hours, and loss of consciousness of less than 30 minutes. This definition is in keeping with the most widely used definitions, which have evolved from multiple working groups, including the American Congress of Rehabilitation Medicine and the World Health Organization.6,7

The exact pathophysiology of mTBI remains under investigation and is a complex biophysical process, as are the mechanisms by which external forces cause damage to the brain. The general pathological process begins immediately following the injury with a significant release of neurotransmitters and concomitant ionic gradient shifts. To restore membrane potentials, energy requirements increase in the setting of mildly reduced blood flow. In mTBI, this does not lead to ischemia. However, anaerobic energy production and subsequent lactic acidosis may ensue.

Findings also suggest that TBI involves damage to the blood-brain barrier.8 Both animal models and postmortem examination of mild brain injury have revealed structural pathological changes, which indicate the presence of microscopic axonal injury.9,10 Diffusion tensor imaging and magnetization transfer imaging can detect subtle changes in white matter integrity following an mTBI.

Several mechanisms of injury contribute to mTBI occurrence. mTBIs in participants in contact sports and among active duty military personel with combat exposure have recently become a focus of attention. In the US, the annual incidence of sport-related mTBI exceeds 1.6 million cases, and up to 10% of returning US Army infantry soldiers have met criteria for mTBI.11,12 The broad pervasiveness of mTBI demonstrated by these figures predicts a high likelihood of psychiatric comorbidities. Indeed, several studies have demonstrated an increased rate of neurobehavioral and psychiatric illness following an mTBI.9,13,14

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Management of Mild Traumatic Brain Injury