GABA alterations in pediatric sport concussion

Abstract

Objective: To evaluate whether frontal-lobe magnetic resonance spectroscopy measures of γ-aminobutyric acid (GABA) would be altered in a sample of adolescents scanned after sport concussion because mild traumatic brain injury is often associated with working memory problems.

Methods: Eleven adolescents (age 14-17 years) who had sustained a first-time sport concussion were studied with MRI/magnetic resonance spectroscopy within 23 to 44 days after injury (mean 30.4 ± 6.1 days). Age- and sex-matched healthy controls, being seen for sports-related injuries not involving the head and with no history of concussion, were also examined. GABA/creatine + phosphocreatine (Cre) was measured in left-sided frontal lobe and central posterior cingulate regions. The frontal voxel was positioned to overlap with patient-specific activation on a 1-back working memory task.

Results: Increased GABA/Cre was shown in the frontal lobe for the concussed group. A decreased relationship was observed in the parietal region. High correlations between GABA/Cre and task activation were observed for the control group in the frontal lobe, a relationship not shown in the concussed participants.

Conclusions: GABA/Cre appears increased in a region colocalized with working memory task activation after sport concussion. Further work extending these results in larger samples and at time points across the injury episode will aid in refining the clinical significance of these observations.

Figure 1. GABA in frontal lobe

(A) Gannet output showing edited spectrum and (B) fitted GABA peak. (C) Concussed participants demonstrated elevated GABA/Cre ratio in frontal lobe as shown on the right. Cre = creatine + phosphocreatine; GABA = γ-aminobutyric acid.

Figure 2. GABA vs fMRI

Plot comparing GABA/Cre and median activation in the frontal voxel for healthy controls (open circles) and concussed participants (solid circles) with linear terms plotted. High concordance is shown between measures in the healthy controls but not for the concussed group. Descriptive examination of concussed individuals who seem to have become shifted off the control regression line did not reveal clear descriptive differences in injury type, location, or severity that would explain the results. Cre = creatine + phosphocreatine; GABA = γ-aminobutyric acid.