Civilians exposed to a blast demonstrate more PCS/PTSD symptoms and reduced white matter connectivity

This article was initially published in the 06/29/23 edition of our Concussion Update newsletter; please consider subscribing.

A study published in BMC Psychiatry found that civilians who had been directly or indirectly exposed to explosive blasts exhibited greater post-concussion syndrome (PCS) and post-traumatic stress disorder (PTSD) symptoms and had reduced white matter (WM) connectivity compared to unexposed civilians. R. Saar-Ashkenazy et al. discuss their two-phase observational study that examines the relationship between blast exposure level, PCS/PTSD symptomatology, cognitive functioning, and white matter connectivity in 305 Beer-Sheva civilians of various blast exposure levels. Rocket attacks–explosions–had previously exposed residential areas in this Israel city to blast impacts. The researchers add that their study “highlights the complexity in differential diagnosis between the two disorders [PCS and PTSD] and may suggest that they are not distinct symptom clusters.”

Over two years, researchers at Soroka University Medical Center in Israel enrolled 289 civilians of different exposure levels (frequency, proximity, direct vs. indirect) to recent blast explosions into Phase 1 of their study, administering questionnaires to gauge exposure levels, demographics, and severity of PCS and PTSD symptoms. Participants who had been directly exposed to a blast had been in a building in “open sightline” to the blast and thus experienced the full blast, while indirectly exposed participants had been in a building obstructed by other buildings from experiencing the full blast. They wished to test whether the severity of PCS and PTSD symptoms is associated with the level of exposure. From participant questionnaires, the authors found that symptom severity is comparable for both direct and indirect exposure groups, although direct exposure participants reported feeling more in danger. Female sex, history of head trauma, and time passed since blast exposure were risk factors for both PCS and PTSD symptoms while being unmarried and feeling scared were risk factors for PCS.

In Phase 2 of their study, they recruited 46 of the previous 289 exposed individuals and 16 new unexposed control participants and administered cognitive and neuroimaging testing to test whether blast exposure was correlated with cognitive ability and white matter connectivity. Compared to unexposed civilians, direct and indirect exposure participants reported greater symptom severity than unexposed participants. In neuroimaging tests, direct exposure participants had reduced WM connectivity compared to indirect exposure and unexposed participants, although cognitive abilities were comparable for all three groups. This suggests that the subjective emotional response is greater for those with direct exposure, but the overall symptom severity for exposed individuals does not depend on the level of exposure. Additionally, exposure to a blast is significantly associated with symptoms of both PCS and PTSD; direct exposure is associated with damage to various white matter tracts in the brain.

The researchers include, “Following our hypothesis, WM connectivity was modulated by exposure to the impact site, with specific WM diffusion alterations occurring in direct-exposed civilians solely… Unlike our hypothesis, these WM diffusion alterations did not correlate with clinical symptoms or with cognitive abilities.”

The authors believe their findings demonstrate that “even if they are not clinically diagnosed, civilians who are directly exposed to explosion blast suffer from mental and WM neuro-anatomical changes and should thus be considered a population at risk for the future development of PTSD and/or PCS.” However, they acknowledge that their study is retrospective and does not draw any causal conclusions. Additionally, future prospective studies with repeated objective and subjective tests may demonstrate how symptomatology can change over time, which may “allow the establishment of biomarkers that would help guide diagnosis and prevention.”