Mild traumatic brain injury (mTBI) is a common injury among military personnel serving in Iraq or Afghanistan. The impact of repeated episodes of combat mTBI is unknown.
To evaluate relationships among mTBI, post-traumatic stress disorder (PTSD) and neurological deficits (NDs) in US veterans who served in Iraq or Afghanistan.
This was a case–control study. From 2091 veterans screened for traumatic brain injury, the authors studied 126 who sustained mTBI with one or more episodes of loss of consciousness (LOC) in combat. Comparison groups: 21 combat veterans who had definite or possible episodes of mTBI without LOC and 21 veterans who sustained mTBI with LOC as civilians.
Among combat veterans with mTBI, 52% had NDs, 66% had PTSD and 50% had PTSD and an ND. Impaired olfaction was the most common ND, found in 65 veterans. The prevalence of an ND or PTSD correlated with the number of mTBI exposures with LOC. The prevalence of an ND or PTSD was >90% for more than five episodes of LOC. Severity of PTSD and impairment of olfaction increased with number of LOC episodes. The prevalence of an ND for the 34 combat veterans with one episode of LOC (4/34=11.8%) was similar to that of the 21 veterans of similar age and educational background who sustained civilian mTBI with one episode of LOC (2/21=9.5%, p-NS).
Impaired olfaction was the most frequently recognised ND. Repeated episodes of combat mTBI were associated with increased likelihood of PTSD and an ND. Combat setting may not increase the likelihood of an ND. Two possible connections between mTBI and PTSD are (1) that circumstances leading to combat mTBI likely involve severe psychological trauma and (2) that altered cerebral functioning following mTBI may increase the likelihood that a traumatic event results in PTSD.
Case–control study of mTBI associated with LOC among US veterans who were deployed to Iraq or Afghanistan during Operations Iraqi Freedom and Enduring Freedom.
Three study groups: (1) 126 veterans who had mTBI with LOC, (2) 21 OIF/OEF veterans who did not suffer mTBI with LOC and (3) 21 veterans who sustained mTBI with LOC in a civilian setting.
Evaluated NDs including a quantitative test of olfaction, PTSD with severity assessed using the PCL-M instrument and a cognitive function using the Montreal Cognitive Assessment Test.
Olfaction was a sensitive test for neurological injury associated with mTBI with LOC.
More episodes of mTBI with LOC were associated with higher prevalence rates of NDs or of PTSD.
The severity of PTSD and extent of olfactory impairment increased with the number of episodes of LOC; cognitive function performance was inversely related to the number of episodes of LOC.
Strengths and limitations of this study
Case–control study of US combat veterans with mTBI who were assessed for NDs, PTSD and cognitive function.
Subjects and comparison groups had detailed assessments for NDs, and combat veterans were also assessed for PTSD.
The findings should be relevant to other groups of military personnel with combat mTBI.
The neurological examination was not blinded.
The selection of veterans in this study may be biased because veterans who do not have health issues may not seek care from the Department of Veterans Affairs.
The comparison groups were small.
The findings in veterans with mTBI with LOC may not apply to people with mTBI without LOC.