Abstract
Mild traumatic brain injury (MTBI) is a vulnerability factor for the development of pain-related conditions above and beyond those related to comorbid traumatic and emotional symptoms. We acquired functional magnetic resonance imaging (fMRI) on a validated pain anticipation task and tested the hypotheses that individuals with a reported history of MTBI, compared with healthy comparison subjects, would show increased brain response to pain anticipation and ineffective pain modulation after controlling for psychiatric symptoms. Eighteen male subjects with a reported history of blast-related MTBI related to combat, and eighteen healthy male subjects with no reported history of MTBI (healthy controls) underwent fMRI during an event-related experimental pain paradigm with cued high or low intensity painful heat stimuli. No subjects in either group met diagnostic criteria for current mood or anxiety disorder. We found that relative to healthy comparison subjects, after controlling for traumatic and depressive symptoms, participants with a reported history of MTBI showed significantly stronger activations within midbrain periaqueductual grey (PAG), right dorsolateral prefrontal cortex and cuneus during pain anticipation. Furthermore, we found that brain injury was a significant moderator of the relationship between anticipatory PAG activation and reported subjective pain. Our results suggest that a potentially disrupted neurocognitive anticipatory network may result from damage to the endogenous pain modulatory system and underlie difficulties with regulatory pain processing following MTBI. In other words, our findings are consistent with a notion that brain injury makes it more difficult to control acute pain. Understanding these mechanisms of dysfunctional acute pain processing following MTBI may help shed light on the underlying causes of increased vulnerability for the development of pain-related conditions in this population.
Highlights
IntroductionThe annual prevalence rate of mild traumatic brain injury (MTBI) in the civilian population in the United States is estimated at 1.3 million (www.cdc.gov/Traumaticbraininjury/statistics.html), and MTBI is considered as a ‘signature injury’ of those involved in Iraq and Afghanistan conflicts.[1,2,3,4]MTBI is a known as vulnerability factor for developing chronic pain in both civilian[5,6] and military[1,7,8] populations
The annual prevalence rate of mild traumatic brain injury (MTBI) in the civilian population in the United States is estimated at 1.3 million, and MTBI is considered as a ‘signature injury’ of those involved in Iraq and Afghanistan conflicts.[1,2,3,4]
Of the regression analysis showed that the interaction term between group (MTBI and healthy controls (HC)) and anticipatory periaqueductual grey (PAG) activation explained a significant increase in variance in subjective pain intensity rating, ΔR2 = 0.21, F (1, 30) = 8.75; P o 0.01
Summary
The annual prevalence rate of mild traumatic brain injury (MTBI) in the civilian population in the United States is estimated at 1.3 million (www.cdc.gov/Traumaticbraininjury/statistics.html), and MTBI is considered as a ‘signature injury’ of those involved in Iraq and Afghanistan conflicts.[1,2,3,4]MTBI is a known as vulnerability factor for developing chronic pain in both civilian[5,6] and military[1,7,8] populations. The annual prevalence rate of mild traumatic brain injury (MTBI) in the civilian population in the United States is estimated at 1.3 million (www.cdc.gov/Traumaticbraininjury/statistics.html), and MTBI is considered as a ‘signature injury’ of those involved in Iraq and Afghanistan conflicts.[1,2,3,4]. Over half of individuals with a history of TBI reported pain-related problems and complaints.[9,10,11,12] Seemingly paradoxically, some—but not all—research suggests this rate to be higher following mild compared with moderate and severe head injury.[5] The most common pain reported is headache and back pain.[12,13,14] Pain symptoms in individuals with a history of MTBI worsen clinical course, interfere with rehabilitative care and markedly increase treatment costs.[15,16,17,18]
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