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

The medical question

Do repeated head impacts in active fighters lead to inflammation in the brain that imaging can detect?

The Fight Medicine Research Institute uses this evidence to frame questions about whether imaging can detect inflammation in the brains of active fighters and whether such findings relate to later symptoms. The study’s small sample and lack of follow-up determine which questions it can inform.

Summary

A PET study of 11 currently active kickboxers and 11 controls found no significant group difference in a marker of inflammation in the brain, although three kickboxers had high values across the brain.

What the work reports

• Kickboxers of the highest competitive rank (rank A), each with at least 20 bouts, and age-matched healthy controls had a PET scan with a tracer that binds to a protein called TSPO, used as a marker of inflammation in the brain. They also had MRI, including diffusion tensor imaging of white matter, and neuropsychological tests. No kickboxer had fought a match or had a concussion within 3 months of the scan.
• The PET measure did not differ significantly between kickboxers and controls in any brain region. Three of the 11 kickboxers had high values in nearly all regions. Those three did not score below the 5th or above the 95th percentile on the neuropsychological tests, and the whole-brain PET measure was not correlated with age, bouts fought, bouts lost, years of training or training frequency.
• On diffusion imaging, one measure (fractional anisotropy) was higher in kickboxers in one white matter region on both sides of the brain, and other regions did not differ significantly. Kickboxers had faster reaction times than controls and did worse on one test of mental flexibility. The authors conclude that the study gives no evidence of a raised inflammation marker in kickboxers as a group, and that the high values in three kickboxers suggest neuroinflammation may be present as a consequence of repetitive head injury.

Limits to keep in mind

• Small and cross-sectional. The authors note that the study has no follow-up information on whether the PET findings relate to the later onset of complaints.
• The authors used years of training, bouts fought, bouts lost and training frequency as stand-ins for exposure to head injury, and say these are not a perfect estimate.
• All participants were without clinical complaints and relatively young, and the tracer is a first-generation one that may be less sensitive than newer tracers. The authors name both as limits.
• 13 kickboxers and 13 controls were included; technical problems with the PET procedure left 11 in each group for analysis.

Publication status and notices

Published in European Journal of Nuclear Medicine and Molecular Imaging, a peer-reviewed journal. Original research article in European Journal of Nuclear Medicine and Molecular Imaging.

Form of this work: Version of record. The version of record is the final article as issued by its publisher.

Crossref and Europe PMC link a published correction to this article: Eur J Nucl Med Mol Imaging. 2022 May;49(6):2103, published online on 11 March 2022. The note in the article says that some reference citations were numbered incorrectly, that two tables and one figure belonged in the supplementary data, and that the original article has been corrected. Linked item.

Crossref and Europe PMC both link a published correction to this article, described above. The full text on PubMed Central is marked as the corrected publication. No retraction notice was found in Crossref or Europe PMC when this record was checked.

Fight Medicine Research Institute contribution

Fight Medicine Research Institute selected and catalogued this study, prepared an original research summary, verified its bibliographic details, and maintains the associated citation record.

PDF files

Article details

Relationship

External research catalogued by the Fight Medicine Research Institute. The original authors, journal and DOI are unchanged.

Published online

15 February 2022

Issue date

July 2022, volume 49, issue 9

Repository date

15 February 2022 (Europe PMC first-publication date)

Date used here

15 February 2022 (Crossref publisher deposit, online publication date)

Rights

CC BY 4.0. Open access under a Creative Commons Attribution licence (CC BY 4.0), as recorded by Europe PMC and the licence link in the source record. The summary on this page is Fight Medicine Research Institute’s own wording. No text or figure from the article is reproduced here. Licence terms.

Source check

12 November 2026, against PubMed Central full text, Crossref and Europe PMC. Checked under the direction of Casey C. Sears, Founder. An LLM was utilized as a research tool with direct human oversight.

Appraisal

The check covered bibliographic details, links, licence and notices. It is not a formal critical appraisal of the full paper.

Clinical review

None. This record is a research summary, not clinical education.

Funding and conflicts

The article states that the authors declare no competing interests. It contains no funding statement.

Catalog

FH-048, added 12 November 2026

Cite the original work

These files cite the work by its own authors, journal and DOI. Fight Medicine Research Institute appears only in a note, as curator of this catalog page.

Gilles N Stormezand, Janine Doorduin, Sandra E Rakers, Jacoba M Spikman, Joukje van der Naalt, David Vállez García, et al.. Imaging of neuroinflammation due to repetitive head injury in currently active kickboxers. European Journal of Nuclear Medicine and Molecular Imaging. 2022;49(9):3162-3172. https://doi.org/10.1007/s00259-022-05715-x

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Related on this website

• Research program: Chronic traumatic encephalopathy (CTE)
• Research priority: Repetitive head impacts and CTE
• Fighter Health: Repetitive head impacts, brain imaging, CTE pathology and TES research