A case-control study examining whether neurological deficits and PTSD in combat veterans are related to episodes of mild TBI

Abstract

Background: 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.

Objective: To evaluate relationships among mTBI, post-traumatic stress disorder (PTSD) and neurological deficits (NDs) in US veterans who served in Iraq or Afghanistan.

Methods: 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.

Results: 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).

Conclusions: 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.

Figure 1

Flow chart of the selection of veterans with episodes of mild traumatic brain injury (mTBI) associated with loss of consciousness (LOC).

Figure 2

Effect of number of episodes of loss of consciousness (LOC) on outcomes for veterans with combat-acquired mild traumatic brain injury: (A) olfaction scores, (B) post-traumatic stress disorder (PTSD) severity as measured by the PCL-M score, (C) score on the Montreal Cognitive Assessment (MOCA) Test and (D) the prevalence of abnormalities on neurological examination (unfilled circles) or PTSD (filled squares). The correlation coefficients for the association between the number of episodes of LOC and the olfaction scores, PCL-M scores and MOCA score are shown in table 2. The straight lines in A, B and C correspond to Kendall's rank correlation analysis coefficients in table 2.

Figure 3

Association of the scores on the Montreal Cognitive Assessment (MOCA) Test with (A) post-traumatic stress disorder (PTSD) severity as measured by the PCL-M score for veterans with PTSD or (B) olfaction scores for veterans with neurological deficits including impaired olfaction. The correlation coefficients for the association between the MOCA scores and the PCL-M scores are shown in table 2. There was no association between MOCA scores and olfaction scores. The straight line in A corresponds to Kendall's rank correlation analysis coefficient in table 2.

Figure 4

Association of the PCL-M and olfaction test scores for veterans with both NDs and post-traumatic stress disorder. The correlation coefficient for the association between the PCL-M scores and olfaction scores is shown in table 2. There was no significant association between PCL-M scores and olfaction scores.