Traumatic Brain Injury and Effects of Altitude - Human Performance ...

Traumatic Brain Injury (TBI) and Effects of Altitude:An Analysis of the Literatureimportance of temperature assessment and stabilization in the pre-hospital setting, especially in militaryoperational settings where casualties may be exposed to extreme hot or cold temperatures and/or highlevels of physical activity for prolonged periods of time.RESEARCH CONSIDERATIONSBased on this review, several key knowledge gap areas are apparent. First and foremost, there is apressing need for additional clinical studies and/or case reports of military aeromedical evacuation andtransport involving TBI casualties. This work is needed to inform the development of risk and injuryprofiles and protocols which address timing and interventions needed to prevent adverse outcomesfrom exposure to altitude-related factors, as well as secondary brain injury events. Goodman et al.(2009) have specified the need for studies to delineate the course of neuro-inflammation during airtransport. Such research may help to identify an “ideal time to fly” so as to avoid exacerbation of post-TBI secondary injury (neuro-inflammatory) events.This review focused on moderate-to-severe TBI patients; none of the studies we identified through thisreview included mTBI patient cohorts for comparison. This is understandable, given that the majority ofmTBI patients recover well over a period of weeks or months without hospitalization. However, itbecomes more difficult to identify severity-related differences across studies that do not wholly addressthe full spectrum of injuries and impact. Observed relationships between severity and altitude-relatedfactors were few (Davis et al., 2005; Diringer et al., 2004; Maggiore et al., 2009; Manley et al., 2001).Military conflicts in high-altitude and mountainous terrain underscore the need for renewed emphasisto determine what if any health risks or performance effects might occur in military personnel whorecover from mTBI, concussion, or multiple concussions and then return to duty at high altitudes.Though recovery from mild head injury is common, mTBI can involve cerebral tissue damage resulting innerve axon degeneration, neurotransmission impairment, and the loss of neural connections (Povlishocket al., 1992; Raghupathi et al., 2002; Smith et al., 2003; Iverson, 2005; Kraus et al., 2007). Quantitatively,the severity of such damage can be conceived as “proportional to the numbers of dead and damagedneurons, their relative functional importance, and their capacity for self-repair” (Gualtieri, 1995). It isreasonable, then, to consider that mTBI also may be adversely affected by exposure to altitude-relatedsecondary injury processes. Most military TBIs are closed-head injuries due to blast or explosion and areclassified as mTBI (Warden, 2006; Galarneau et al., 2008). Many military personnel who sustain mTBI orconcussion will recover and return to duty. Lew et al. (2007) present an informative review of postconcussionreturn-to-action criteria based on research and experience from within the field of sportsmedicine. However, little research has addressed the question of lingering, subclinical functionalimpairments since the early work of Ewing, et.al. (1980). Military conflicts in high-altitude andmountainous terrain underscore the need for renewed emphasis to determine what if any health risksor performance effects might occur in military personnel who recover from mTBI, concussion or multipleconcussions and then return to duty at high altitudes.Finally, research is needed to investigate the prophylactic and/or therapeutic effects of drug therapiescommonly used to treat altitude-related illness, to determine their potential efficacy in preventingaltitude-related illness or injury in TBI casualties. To the extent that such medications improveoxygenation or reduce inflammatory responses, they may also be helpful to prevent or mitigatesecondary brain injury generally. Likewise, it is important to identify any such formulations that may beSeptember 14, 2010 26