Combat TBI: History, Epidemiology, and Injury Modes

Abstract

Although types and modes of combat injury have changed over the centuries as weapons of war evolved, details about combat traumatic brain injury (TBI) date from the earliest accounts of warfare. This chapter provides a brief historical overview of combat TBI resulting from primitive blunt and penetrating head injuries to current blast-related injuries. Updated numbers of TBI events and injuring mechanisms will be considered. Brain injury causes loss or alteration of consciousness, prograde and retrograde amnesia, and immediate physical and neurological effects ranging from mild to severe. These injuries, in certain cases, cause varying chronic physical, cognitive, and behavioral issues. The most common form of brain injury, acute mild TBI or concussion (mTBI/concussion), has multiple definitions derived from various sources. Vasterling et al. have provided a useful summary of these iterations (Vasterling, 2012).The operative definition selected for this review includes loss or alteration consciousness for up to 30 minutes at the time of injury, a confused or disoriented state lasting less than 24 hours, memory loss lasting less than 24 hours, and normal structural brain imaging on computed tomographic scanning. Glasgow Coma Scale scores of 13–15 characterize acute mTBI, whereas lower Glasgow Coma Scale scores, 9–12, designate acute moderate TBI. Glasgow Coma Scale scores of 3–8 designate acute severe TBI (Teasdale and Jennett, 1974). Current combat or military TBI/concussions most frequently are classified as mild. Although recovery from mTBI/concussion is said to be the norm, in about 15% (estimates range from 10%–25%) of cases, physical disabilities and symptoms persist beyond three months to become a chronic condition, also known as postconcussion syndrome (Vasterling, 2012). Chronic sequelae of postconcussion syndrome include headache, insomnia, fatigue, sensory, balance, and other neurologic defects as well as cognitive and emotional disorders. Symptoms can be subtle and variable in severity and frequency over time; mTBI and concussion are often used clinically as synonyms. This chapter focuses on mTBI/concussion as a combat injury.Diagnosis of posttraumatic stress disorder (PTSD), first accepted as a formal diagnosis in 1980 (Horowitz et al., 1980), and other mental illness including depression are reportedly more common in combatants as compared with nondeployed service members during current ongoing military operations (Blakely, 2013). The methods used to obtain estimates affect data concerning numbers of cases of TBI, PTSD, and other mental disorders. Individuals usually are reported only once as a case within a category; data can be presented as the number of diagnoses (prevalence), rate of new diagnoses in a population (incidence), or total number of cases in a population. The total number of diagnoses changes in relation to population size, which for military conditions increases over time with continued combat activities (Blakely, 2013). This chapter uses numbers available from public sources for the Department of Defense (DOD) and updated data through 2013 from the tracking tool used by the Department of Veterans Affairs (VA).PTSD results from exposure to a traumatic event with risk of serious injury or bodily harm to self or others and a response to that event involving intense fear, horror, or helplessness. Symptoms include reexperiencing of the traumatic event, including nightmares and distressing recollections, avoidance of stimuli associated with the trauma with diminished responsiveness and loss of interest in activities, and hyperarousal including irritability, anger, hypervigilance, insomnia, and concentration difficulties. Cognitive and behavioral symptoms of PTSD and depression overlap with those of mTBI; mTBI sustained during the stress of battle is believed to predispose to or accentuate PTSD (Bryant, 2011; Vasterling, 2012).Historical narratives reveal connections or associations between past and current relationships (Rabins, 2013). Vignettes from past and present conflicts yield insights into the causes and sequelae of combat injuries affecting the brain. Currently, blast injuries predominate among combatants in Operations Enduring Freedom, Iraqi Freedom, and New Dawn (OEF/OIF/OND). Recognition of the importance of mTBI and PTSD relates to enhanced surveillance and clinical guidelines initiated by the DOD and the VA (Management of Concussion/mTBI Working Group 2009). Incidence and prevalence data from both sources provide ongoing estimates of the numbers of service members affected by TBI; the frequency of this particular injury has become a matter of increasing concern. Although the long-term effects of brain damage caused by differing modes of head injury seem to appear identical in the long term (Belanger et al., 2009), recent observations suggest that differing modes of combat injury—for example, blunt as compared with blast injuries—result in differing vestibular-ocular and spinal reflexes (Hoffer et al., 2009) and neural activation responses (Fischer et al., 2013). Behavioral disorders appear to be more common with blast as opposed to blunt injury (Mendez et al., 2013). Repeated injuries, particularly sports-related, have become a public health concern because of their long-term consequences (Jordan, 2013). These emerging observations are important for assessing treatments, outcomes, and disability determinations.