Evidence for Beneficial and Adverse Effects of Alcohol in Animal Models and Clinical Studies of Traumatic Brain Injury

Abstract

There is no doubt that acute and/or chronic alcohol consumption contributes to the incidence of traumatic brain injury (TBI). However, more than three decades of research on the impact of alcohol on the pathophysiological, neuroanatomical and functional outcomes of TBI have produced inconsistent results. In this chapter, the authors summarize the primary outcomes reported in the majority of animal studies and a great number of clinical studies that have been conducted in these areas. Studies reporting beneficial or adverse effects of acute alcohol treatment in animal models of experimental TBI are reviewed first, followed by those animal studies reporting on the effects of chronic or repeated alcohol exposures. Clinical studies on short-term outcomes such as morbidity, complications or mortality during acute care that have been associated with a positive admission blood alcohol content are then summarized, where the majority of studies have indicated beneficial or null effects of alcohol while fewer indicate injury exacerbation or worsened outcomes. Finally, clinical studies that have examined the impact of a history of preinjury alcohol abuse on TBI outcomes and those clinical studies that have focused more on functional outcomes are reviewed.Alcohol intoxication increases the risk of occurrence of multiple types of injury, including TBI, and may affect the morbidity and mortality associated with head injury. Reviews of the literature have indicated that between 25% and 51% of TBI patients were intoxicated at the time of injury (Corrigan, 1995; Parry-Jones et al., 2006; Tien et al., 2006). In animal models of TBI, alcohol has been shown to produce both adverse and neuroprotective effects, whereas clinical studies assessing acute and the long-term neurological and behavioral impact of intoxication demonstrate no consistent effects (Asmaro et al., 2013; Chen et al., 2012; Opreanu et al., 2010). Such discrepancies may be due to the numerous dose-related effects of alcohol, the time of exposure in relation to the injury, and the nature of the injury and its outcome(s). The aim of this chapter is to systemically review animal and clinical studies on ethanol (EtOH) and TBI focusing on these elements to determine whether any specific pattern of interaction emerges.