Associations Between Brain Metabolites Measured With MR Spectroscopy and Head Impacts in High School American Football Athletes.

Background: While changes in brain metabolites after injury have been reported, relationships between metabolite changes and head impacts are less characterized.

Purpose: To investigate alterations in neurochemistry in high school athletes as a function of head impacts, concussion, and the use of a jugular vein compression (JVC) collar.

Study type: Prospective controlled trial.

Subjects: A total of 284 male American football players, divided into JVC collar and noncollar groups; 215 included in final analysis (age = 15.9 ± 1.0 years; 114 in collar group).

Field strength/sequence: 3 Tesla/T₁-weighted gradient echo, ¹H point resolved spectroscopy, acquired between August and November 2018.

Assessment: Head impacts were quantified using accelerometers. Concussion was diagnosed by medical professionals for each team. Pre- to postseason differences in total N-acetylaspartate (tNAA), total choline (tCho), myo-inositol (myoI), and glutamate + glutamine (Glx), in primary motor cortex (M1) and anterior cingulate cortex (ACC), relative to total creatine (tCr), were determined.

Statistical tests: Group-wise comparisons were performed using Wilcoxon signed-rank, Friedman's, and Mann-Whitney U tests. Relationships between ∆metabolite/tCr and mean g-force were analyzed using linear regressions accounting for concussion and JVC collar. Significance was set at P ≤ 0.05.

Results: In participants without concussion, a significant decrease in tCho/tCr (0.233 ± 1.40 × 10^-3 to 0.227 ± 1.47 × 10^-7) and increase in Glx/tCr (1.60 ± 8.75 × 10^-3 to 1.63 ± 1.08 × 10^-2) in ACC were observed pre- to postseason. The relationship between ∆tCho/tCr in M1 and ACC and mean g-force from >80 g to >140 g differed significantly between participants with and without concussion (M1 β ranged from 3.9 × 10^-3 to 2.1 × 10^-3; ACC β ranged from 2.7 × 10^-3 to 2.1 × 10^-3). Posthoc analyses revealed increased tCho/tCr in M1 was positively associated with mean g-force >100 g (β = 3.6 × 10^-3) and >110 g (β = 2.9 × 10^-3) in participants with concussion. Significant associations between $∆\text{myoI}/\mathrm{tCr}$ in ACC and mean g-force >110 g (β = -1.1 × 10^-3) and >120 g (β = -1.1 × 10^-3) were observed in the collar group only.

Data conclusion: Diagnosed concussion and the use of a JVC collar result in distinct neurochemical trends after repeated head impacts.

Level of evidence: 2 TECHNICAL EFFICACY: Stage 3.