Neurometabolic Changes in the Acute Phase after Sports Concussions Correlate with Symptom Severity

Abstract

Sports concussion is a major problem that affects thousands of people in North America every year. Despite negative neuroimaging findings, many athletes display neurophysiological alterations and post-concussion symptoms such as headaches and sensitivity to light and noise. It is suspected that neurometabolic changes may underlie these changes. In this study we investigated the effects of sports concussion on brain metabolism using (1)H-MR spectroscopy by comparing a group of 12 non-concussed athletes with a group of 12 concussed athletes of the same age (mean 22.5 years) and education (mean 16 years). All athletes were scanned 1-6 days post-concussion in a 3T Siemens MRI, and were administered a symptom scale to evaluate post-concussion symptomatology. Participants also completed a neuropsychological test battery to assess verbal memory, visual memory, information processing speed, and reaction time, and no group differences were detected relative to controls. Concussed athletes showed a higher number of symptoms than non-concussed athletes, and they also showed a significant decrease in glutamate in the primary motor cortex (M1), as well as significant decreases in N-acetylaspartate in the prefrontal and primary motor cortices. No changes were observed in the hippocampus. Furthermore, the metabolic changes in M1 correlated with self-reported symptom severity despite equivalent neuropsychological performance. These results confirm cortical neurometabolic changes in the acute post-concussion phase, and demonstrate for the first time a correlation between subjective self-reported symptoms and objective physical changes that may be related to increased vulnerability of the concussed brain.