Increased T2 Relaxometry in Mild Traumatic Brain Injury: An Individualised Marker of Acute Neuroinflammation?

Mild traumatic brain injury (mTBI), often called concussion, is a prevalent condition that can have significant implications for people’s health, functioning and well-being. Current clinical practice relies on self-reported symptoms to inform return to sport, work or school decisions, which can be highly problematic. An objective technique to detect the impact of mTBI on the brain is needed. MRI-based T2 relaxation is a quantitative imaging technique that is susceptible to detecting fluid properties in the brain and is a promising marker for detecting subtle neuroinflammation. This study aimed to investigate the potential of T2 relaxometry MRI in assessing mTBI at the individual level. The current study included 20 male participants with acute sports-related mTBI (within 14 days post-injury) and 44 healthy controls. We statistically compared each mTBI participant’s voxel-wise T2 relaxometry map with the average of controls using a voxel-wise z-test with false discovery rate correction. In addition, five participants were re-scanned after clinical recovery, and their acute scans were compared to their recovery scans. Results revealed significantly increased T2 relaxation times in 19/20 (95%) of mTBI individuals, compared to controls, in multiple regions, including the hippocampus, frontal cortex, parietal cortex, insula, cingulate cortex and cerebellum. This suggests the presence of increased cerebral fluid in individuals with mTBI. Longitudinal results indicated a partial reduction in T2 relaxation for all five participants, suggesting a resolution over time. This research highlights the potential of T2 relaxometry MRI as a non-invasive method for assessing neuroinflammation in mTBI. Identifying and monitoring neuroinflammation could aid in predicting recovery and developing individualised treatment plans for individuals with mTBI. Future research would benefit from repeating all MRI scans at recovery to evaluate whether T2-relaxometry normalises or persists. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Health Research Council of New Zealand (HRC) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Health and Disability Ethics Committee of New Zealand gave ethical approval for this work (HDEC 2022 EXP 11078) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors Data can be made available by request to the corresponding author.