Imaging of neuroinflammation due to repetitive head injury in currently active kickboxers

PURPOSE: Chronic traumatic encephalopathy refers to a neurodegenerative disease resulting from repetitive head injury of participants in contact sports. Similar to other neurodegenerative diseases, neuroinflammation is thought to play a role in the onset and progression of the disease. Limited knowledge is available regarding the neuroinflammatory consequences of repetitive head injury in currently active contact sports athletes. PET imaging of the 18-kDa translocator protein (TSPO) allows quantification of microglial activation in vivo, a marker of neuroinflammation. METHODS: Eleven rank A kickboxers and 11 age-matched controls underwent TSPO PET using [(11)C]-PK11195, anatomical MRI, diffusion tensor imaging, and neuropsychological testing. Relevant imaging parameters were derived and correlated with the outcomes of the neuropsychological testing. RESULTS: On a group level, no statistically significant differences were detected in non-displaceable binding potential (BP(ND)) using PET. Individually, 3 kickboxers showed increased BP(ND)s in widespread regions of the brain without a correlation with other modalities. Increased FA was observed in the superior corona radiata bilaterally. DTI parameters in other regions did not differ between groups. CONCLUSION: Despite negative results on a group level, individual results suggest that neuroinflammation may be present as a consequence of repetitive head injury in active kickboxers. Future studies using a longitudinal design may determine whether the observed TSPO upregulation is related to the future development of neuropsychiatric symptoms. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00259-022-05715-x.