1) Koerte IK, Ertl-Wagner B, Reiser M, Zafonte R, Shenton ME. White Matter Integrity in the Brains of Professional Soccer Players Without Symptomatic Concussion. JAMA. 2012 Nov 14; 308(18): 1859-61. doi: 10.1001/jama.2012.13735. PMID: 23150002
This study was the first to report brain alterations in a small sample of soccer players exposed to repetitive head impacts. Although only participants without previous symptomatic concussion were included, advanced neuroimaging revealed widespread increase in radial diffusivity in soccer players, consistent with findings observed in patients with mTBI, and suggesting possible demyelination. (Featured in New York Times, Time Magazine, and numerous other media reports).
2) Sollmann N, Echlin PS, Schultz V, Viher PV, Lyall AE, Tripodis Y, Kaufmann D, Hartl E, Kinzel P, Forwell LA, Johnson AM, Skopelja EN, Lepage C, Bouix S, Pasternak O, Lin AP, Shenton ME, Koerte IK. Sex differences in white matter alterations following repetitive subconcussive head impacts in collegiate ice hockey players. Neuroimage Clin. 2017 Nov 21;17:642-649. PMID: 29204342
This study was the first to report sex-specific differences in brain structural changes over the course of a play season of collegiate ice hockey exposed to repetitive head impacts. Diffusion tensor imaging showed large brain regions where female athletes experienced different changes in brain microstructure compared to their male counterparts suggesting that there are likely sex-specific differences in the effect of repetitive head impacts.
3) Koerte IK, Nichols E, Tripodis Y, Schultz V, Lehner S, Igbinoba R, Chuang AZ, Mayinger M, Klier E, Muehlmann M, Kaufmann D, Lepage C, Heinen F, Schulte-Koerne G, Zafonte RD, Shenton ME, Sereno AB. Impaired Cognitive Performance in Youth Athletes Exposed to Repetitive Head Impacts. J Neurotrauma. 2017 Aug 15; 34(16): 2389-2395 PMID: 28381107
Youth athletes experienced a decrease in their reaction time and cognitive function immediately after a training session in their sport underlining the benefits of physical workout for the brain. However, while athletes of a non-contact sport yielded improvement in their reaction time and cognitive function over the period of a play season, youth soccer players did not show an improvement in their cognitive function suggesting a negative effect of exposure to repetitive head impacts.
4) Koerte IK, Kaufmann D, Hartl E, Bouix S, Pasternak O, Kubicki M, Forwell LA, Johnson AM, Echlin PS, Shenton ME. A Prospective Study of Physician-Observed Concussion During a Varsity University Hockey Season: Part 2 of 4: White Matter Integrity in Ice Hockey Players. Neurosurg Focus. 2012 Dec; 33(6): E3. doi: 10.3171/2012.10.FOCUS12303. PMID: 23199426
DTI revealed changes in WM diffusivity in ice hockey players over the course of one season that are likely due to subconcussive and concussive brain trauma. Concussed athletes showed the most pronounced changes over the course of one season. (Featured in numerous online news outlets including New York Times).
5) Koerte IK, Mayinger M, Muehlmann M, Kaufmann D, Lin AP, Steffinger D, Fisch B, Rauchmann B, Immler S, Karch S, Heinen F, Ertl-Wagner B, Reiser M, Stern R, Zafonte RD, Shenton ME. Cortical Thinning in Former Professional Soccer Players. Brain Imaging Behav. 2016 Sept; 10(3): 792-8. doi: 10.1007/s11682-015-9442-0. PMID: 26286826.
Former professional soccer players showed increased cortical thinning with age. This cortical thinning was associated with the estimated exposure to repetitive head impacts while heading the ball in soccer. Although within the normal range, soccer players showed decreased cognitive function compared to controls potentially indicating early cognitive decline. (Featured in numerous European news outlets).
6) Pasternak O, Koerte IK, Bouix S, Fredman E, Sasaki T, Mayinger M, Helmer KG, Johnson AM, Holmes JD, Forwell LA, Skopelja EN, Shenton ME, Echlin PS. Hockey Concussion Education Project, Part 2. Microstructural White Matter Alterations in Acutely Concussed Ice Hockey Players: A Longitudinal Free-Water MRI Study. J Neurosurg. 2014 Apr; 120(4):873-81. doi: 10.3171/2013.12.JNS132090. PMID: 24490785
Concussion during ice hockey games results in microstructural alterations that are detectable using dMRI. The alterations found suggest decreased extracellular space and decreased diffusivities in WM tissue indicative of swelling and/or by increased cellularity of glia cells. This paper is important because it established a clearer picture of how the brain responds to concussion.
7) Kikinis Z, Muehlmann M, Pasternak O, Peled S, Kulkarni P, Ferris C, Bouix S, Rathi Y, Koerte IK, Pieper S, Yarmarkovich A, Porter CL, Kristal BS, Shenton ME. Diffusion imaging of mild traumatic brain injury in the impact accelerated rodent model: A pilot study. Brain Inj. 2017 Jun 19:1-6. doi: 10.1080/02699052.2017.1318450. [Epub ahead of print] PMID:28627942
This study investigated the processes occurring 1 week after injury at the time of regeneration and degeneration using dMRI in the impact acceleration rat mTBI model. Seven days post-injury, during the period of tissue reparation, microstructural changes to WM can be detected using dMRI.
8) Koerte IK*, Lin AP*, Muehlmann, M, Merugumala S, Liao HJ, Starr T, Kaufmann D, Mayinger M, Steffinger D, Fisch B, Karch S, Heinen F, Ertl-Wagner B, Reiser M, Stern RA, Zafonte R, Shenton ME. Altered Neurochemistry in Former Professional Soccer Players Without a History of Concussion. J Neurotrauma. 2015 Sept 1; 32(17): 1287-93. doi: 10.1089/neu.2014.3715. PMID: 25843317 (* shared first authorship) (Featured in numerous European newspapers)
Results of this study suggest a possible association between repetitive subconcussive head impacts from heading the ball in soccer, and neuroinflammation, in former professional soccer players, compared with athletic controls. Future studies, including longitudinal analyses, are needed to clarify the time course underlying changes in neurochemistry, as well as in the association of these changes with neurocognition, motor functioning, and quality of life.