A Systematic Review of Structural and Functional Imaging Correlates of Headache or Pain after Mild Traumatic Brain Injury.

Headaches and pain-related symptoms are the most disabling somatic complaints following mild traumatic brain injury (mTBI). In this study, we reviewed the existing literature examining structural differences in brain morphology and axonal connections, as well as functional differences in brain activity and connectivity associated with pain or post-traumatic headache (PTH) following mTBI. We searched MEDLINE®, Embase, PubMed, Cumulative Index of Nursing and Allied Health Literature (CINAHL), Cochrane Central Register of Controlled Trials, and Web of Science databases for: (1) TBI OR concussion OR post-concussion syndrome; (2) pain OR headache; and (3) magnetic resonance imaging OR functional MRI OR diffusion tensor imaging. Inclusion criteria were that articles be original studies written in English about participants with mTBI or concussion diagnosis with results reported about pain and/or headache. Excluded were review articles, case studies, documentaries, and studies related to moderate to severe TBI. Quality was assessed using the Newcastle-Ottawa Scale (NOS) quality assessment tool. Nineteen out of 3439 studies satisfied the inclusion and exclusion criteria. Participants with pain-related symptoms had lower cortical thickness in frontal and parietal cortical areas and spinothalamic tract volume. Differences in axonal connectivity were displayed in the corpus callosum, spinothalamic tract, fornix-septohippocampal circuit, and periaqueductal gray. Less activation in pain-related regions during a heat-pain task-based fMRI was reported in participants with PTH. In conclusion, individuals with pain following mTBI display differences in brain structure and brain function, suggesting irregularities in the descending pain modulatory system. These findings primarily provide information on neuroimaging differences in adults; there is limited research in pediatric populations.