Progressive outer midbrain lesion associated with repetitive mild traumatic brain injury: a study of 52 professional wrestlers.

Authors

Akihiro Yamamoto, Manabu Sasaki, Yasukazu Hijikata, Koshi Ninomiya, Koichi Hosomi, Taro Shimono, Shunji Asamoto, Haruhiko Kishima

Published in

Journal of neurosurgery. Pages 1-8. Nov 06, 2026. Epub Nov 06, 2026.

Abstract

Finite element modeling studies suggest that the midbrain is susceptible to mechanical strain during mild traumatic brain injury (mTBI), but clinical neuroimaging characterization of midbrain alterations associated with mTBI remains limited. In 2018, the authors identified lesions on T2-weighted MRI consistently localized in the lateral midbrain tegmentum of some veteran professional Japanese wrestlers. These lesions were termed outer midbrain lesions (OMLs). This study aimed to elucidate the relationship between mTBI and OMLs.
The study included 52 male Japanese professional wrestlers who underwent brain MRI examinations in 2022. An OML was defined as a lesion with a diameter ≥ 2 mm. Longitudinal changes in OMLs were examined in wrestlers who had undergone MRI before 2022. As a control group, brain MRI data from 91 patients with spinal cord injury or central poststroke pain from the authors' prior study were reviewed for the presence of OMLs. Wrestling career length was investigated as a surrogate for the period of repetitive head impact. Histories of concussion and symptomatic mTBI were reviewed from the records maintained by exclusive trainers.
OMLs were identified in 12 wrestlers (23.1%). Traumatic lesions were not observed in other parts of the brain. OMLs were identified only in wrestlers older than 40 years, whereas they were absent in the control group, even among older individuals. OMLs exhibited progressive growth over time on longitudinal MRI. The presence of OMLs was not associated with a documented history of symptomatic mTBI, but with career length. Each additional year of participation in professional wrestling was associated with a 14% increase in the prevalence of OMLs (prevalence ratio 1.14, 95% CI 1.08-1.19).
OMLs are neural structural alterations strongly suggested to be associated with repeated asymptomatic mTBI. To the best of the authors' knowledge, this is the first study to demonstrate the susceptibility of the midbrain to mTBI based on real-world clinical findings.

PMID:
42993951
Bibliographic data and abstract were imported from PubMed on 07 Nov 2026.

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