Objective: Recent studies have shown, in asymptomatic concussed athletes, metabolic disruption in the primary motor cortex (M1) and abnormal intracortical inhibition lasting for more than six months. The present study aims to assess if these neurochemical and neurophysiological alterations are persistent and linked to M1 cortical thickness. Methods: Sixteen active football players who sustained their last concussion, on average, three years prior to testing and 14 active football players who never sustained a concussion were recruited for a single session of proton magnetic resonance spectroscopy (1H-MRS) and transcranial magnetic stimulation (TMS). Measures of M1 and whole brain cortical thickness were acquired, and 1H-MRS data were acquired from left M1 using a MEGA-PRESS sequence. Cortical silent period (CSP) and long-interval intracortical inhibition (LICI) were measured with TMS applied over left M1. Results: No significant group differences were observed for metabolic concentrations, TMS measures, and cortical thickness. However, whereas GABA and glutamate levels were positively correlated in control athletes, this relationship was absent in concussed athletes. Conclusion: These data suggest the general absence of neurophysiologic, neurometabolic and neuroanatomical disruptions in M1 three years following the last concussive event. However, correlational analyses suggest the presence of a slight metabolic imbalance between GABA and glutamate concentrations in the primary motor cortex of concussed athletes. Significance: The present study highlights the importance of multimodal assesments of the impacts of sport concussions.
Bibliographical noteFunding Information:
This work was supported by grants from the Canadian Institutes of Health Research and the Fonds de Recheche du Québec – Santé to H.T. and M.L. M.M. acknowledges the support from Biotechnology Research Center (BTRC) grant P41 RR008079 and P41 EB015894 (NIBIB), and NCC P30 NS076408.The authors would like to thank Edward J. Auerbach, Ph.D. (Center for Magnetic Resonance Research, University of Minnesota) for implementing MEGA-PRESS sequence on Siemens, and Romain Valabregue, Ph.D. (Centre de NeuroImagerie de Recherche, Paris, France) and Brice Tiret, Ing (Unité de neuroimagerie fonctionnelle, Montréal) for developing processing tools.
- Magnetic resonance spectroscopy
- Sport concussion
- Transcranial magnetic stimulation
- Traumatic brain injury