Update on TBI and Cognitive Impairment in Military Veterans
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Traumatic brain injury (TBI) is a common cause of morbidity and mortality in military life. Interest in military TBI has increased recently due to the conflicts in Iraq and Afghanistan. Certain types of TBI are relatively unique to the military, the most prominent being blast-related TBI. Blast-related mild TBI has been of particular concern in veterans from the most recent conflicts although controversy remains concerning its separation from post-traumatic stress disorder. TBI is also a risk factor for the later development of neurodegenerative diseases in which cognitive impairment is prominent putting veterans at risk for disorders including Alzheimer’s disease and chronic traumatic encephalopathy. Recent evidence associating TBI with chronic cognitive impairment is reviewed in the context of its relevance to military veterans.
KeywordsAlzheimer’s disease Blast Chronic traumatic encephalopathy Dementia Traumatic brain injury Military veterans
The author has received research support from the Department of Veterans Affairs, Veterans Health Administration, Rehabilitation Research and Development Service Awards 1I01RX000179-01 and 1I01RX000996-01.
Compliance with Ethics Guidelines
Conflict of Interest
Gregory A. Elder has received research grants from the Veterans Administration.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Papers of particular interest, published recently, have been highlighted as: • Of importance
- 3.Gubata ME, Packnett ER, Blandford CD, Piccirillo AL, Niebuhr DW, Cowan DN. Trends in the epidemiology of disability related to traumatic brain injury in the US Army and Marine Corps: 2005 to 2010. J Head Trauma Rehabil. 2014;29(1):65–75. doi: 10.1097/HTR.0b013e318295f590.CrossRefPubMedGoogle Scholar
- 5.DePalma RG. TBI combat history, epidemiology and injury modes. In: Kobeissy F, editor. Brain neurotrauma: molecular, neuropsychological, and rehabilitation aspects. Boca Raton FL, USA: CRC Press; 2015. p. 5–14.Google Scholar
- 8.Defense and Veterans Brain Injury Center. http://dvbic.dcoe.mil/dod-worldwide-numbers-tbi. Accessed July 12, 2015
- 14.Tanielian T, Jaycox LH, editors. Invisible wounds of War: psychological and cognitive injuries, their consequences, and services to assist recovery. Santa Monica, CA: Rand Corporation; 2008.Google Scholar
- 16.•Chase RP, Nevin RL. Population estimates of undocumented incident traumatic brain injuries among combat-deployed US military personnel. J Head Trauma Rehabil. 2015;30(1):E57–64. doi: 10.1097/HTR.0000000000000061. Documents the high incidence of unrecognized TBIs suffered by U.S. troops deployed to Iraq or Afghanistan during the period of January 2003 to October 2006.CrossRefPubMedGoogle Scholar
- 18.Military Acute Concussion Evaluation (MACE). https://www.jsomonline.org/TBI/MACE_Revised_2012.pdf. Accessed July 12, 2015.
- 24.Evans CT, St Andre JR, Pape TL, Steiner ML, Stroupe KT, Hogan TP, et al. An evaluation of the veterans affairs traumatic brain injury screening process among operation enduring freedom and/or operation Iraqi freedom veterans. PM R. 2013;5(3):210–20. doi: 10.1016/j.pmrj.2012.12.004.CrossRefPubMedGoogle Scholar
- 26.United States Department of Veterans Affairs. http://www.polytrauma.va.gov. Accessed July 12, 2015.
- 33.•Elder GA, Stone JR, Ahlers ST. Effects of low-level blast exposure on the nervous system: is there really a controversy? Front Neurol. 2014;5:269. doi: 10.3389/fneur.2014.00269. 10.3389/fneur.2014.00269. Reviews the mTBI/PTSD controversy as well as animal and human literature on the effects of low level blast.PubMedCentralCrossRefPubMedGoogle Scholar
- 36.IOM (Institute of Medicine). Gulf War and health: Long-term effects of blast exposures. Washington, DC2014.Google Scholar
- 40.•Elder GA, Dorr NP, De Gasperi R, Gama Sosa MA, Shaughness MC, Maudlin-Jeronimo E, et al. Blast exposure induces post-traumatic stress disorder-related traits in a rat model of mild traumatic brain injury. J Neurotrauma. 2012;29(16):2564–75. doi: 10.1089/neu.2012.2510. Demonstrates that low-level blast exposure in rats can induce PTSD-related behavioral traits in the absence of a psychological stressor.PubMedCentralCrossRefPubMedGoogle Scholar
- 41.•Brenner LA, Homaifar BY, Olson-Madden JH, Nagamoto HT, Huggins J, Schneider AL, et al. Prevalence and screening of traumatic brain injury among veterans seeking mental health services. J Head Trauma Rehabil. 2013;28(1):21–30. doi: 10.1097/HTR.0b013e31827df0b5. Study examining the frequency of a history of TBI among veterans seeking mental health services at a VA facility. 45% of those seeking treatment had suffered a probable TBI.CrossRefPubMedGoogle Scholar
- 48.National Research Council. Gulf War and health: volume 7: long-term consequences of traumatic brain injury. Washington, DC: The National Academies Press; 2008.Google Scholar
- 51.•Budde MD, Shah A, McCrea M, Cullinan WE, Pintar FA, Stemper BD. Primary blast traumatic brain injury in the rat: relating diffusion tensor imaging and behavior. Front Neurol 2. 2013;4:154. doi: 10.3389/fneur.2013.00154. Study examining diffusion tensor imaging (DTI) after a blast injury in rats. Region specific decreases in fractional anisotropy were found that expanded during a 4 to 30 day observation period suggesting an evolving lesion.Google Scholar
- 57.•McKee AC, Stern RA, Nowinski CJ, Stein TD, Alvarez VE, Daneshvar DH, et al. The spectrum of disease in chronic traumatic encephalopathy. Brain. 2013;136(Pt 1):43–64. doi: 10.1093/brain/aws307. Describes the features of CTE in 68 cases including 21 military veterans.PubMedCentralCrossRefPubMedGoogle Scholar
- 58.•Omalu B, Hammers JL, Bailes J, Hamilton RL, Kamboh MI, Webster G, et al. Chronic traumatic encephalopathy in an Iraqi war veteran with posttraumatic stress disorder who committed suicide. Neurosurgical focus. 2011;31(5):E3. doi: 10.3171/2011.9.FOCUS11178. Describes the first case of CTE in an Iraq veteran.CrossRefPubMedGoogle Scholar
- 59.•Goldstein LE, Fisher AM, Tagge CA, Zhang XL, Velisek L, Sullivan JA, et al. Chronic traumatic encephalopathy in blast-exposed military veterans and a blast neurotrauma mouse model. Sci Transl Med. 2012;4(134):134ra60. doi: 10.1126/scitranslmed.3003716. Describes four cases of CTE in Iraq and Afghanistan veterans along with prominant tau pathology in an animal model of blast injury.PubMedCentralCrossRefPubMedGoogle Scholar
- 60.Huber BR, Meabon JS, Martin TJ, Mourad PD, Bennett R, Kraemer BC, et al. Blast exposure causes early and persistent aberrant phospho- and cleaved-tau expression in a murine model of mild blast-induced traumatic brain injury. J Alzheimers Dis. 2013;37(2):309–23. doi: 10.3233/JAD-130182.PubMedCentralPubMedGoogle Scholar
- 69.•De Gasperi R, Gama Sosa MA, Kim SH, Steele JW, Shaughness MC, Maudlin-Jeronimo E, et al. Acute blast injury reduces brain abeta in two rodent species. Front Neurol. 2012;3:177. doi: 10.3389/fneur.2012.00177. Describes the acute lowering of brain Abeta following blast injury in animals.PubMedCentralCrossRefPubMedGoogle Scholar
- 71.•Tweedie D, Rachmany L, Rubovitch V, Zhang Y, Becker KG, Perez E, et al. Changes in mouse cognition and hippocampal gene expression observed in a mild physical- and blast-traumatic brain injury. Neurobiol Dis. 2013;54:1–11. doi: 10.1016/j.nbd.2013.02.006. Examined changes in the mouse hippocampal transcriptome following a weight drop injury or exposure to a low-level blast. While a common set of up regulated or down regulated RNAs were found, most changes between the two models differed. A functional pathway analysis found that genes up regulated or down regulated in AD were regulated in similar directions by non-blast TBI but in the opposite direction after blast.PubMedCentralCrossRefPubMedGoogle Scholar
- 76.IOM (Institute of Medicine). Amyotrophic Lateral Sclerosis in Veterans: Review of the Scientific Literature. Washington DC 2006.Google Scholar
- 77.Department of Veterans Affairs. Presumption of Service Connection for Amyotrophic Lateral Sclerosis. Federal Registry 2009. p. 57072.Google Scholar
- 78.•Faden AI, Loane DJ. Chronic neurodegeneration after traumatic brain injury: Alzheimer disease, chronic traumatic encephalopathy, or persistent neuroinflammation? Neurotherapeutics. 2015;12(1):143–50. doi: 10.1007/s13311-014-0319-5. Reviews the evidence for inflammation playing a role in chronic neurodegeneration after TBI.CrossRefPubMedGoogle Scholar