In vivo detection of acute pain-induced changes of GABA+ and Glx in the human brain by using functional 1H MEGA-PRESS MR spectroscopy

Abstract

In vivo(1)H MR spectroscopic detection of pain associated metabolic changes in the human brain may allow for an objective evaluation of the perceived pain intensity and assessment of the involved neurotransmitters. Ultimately, it may lead to a deeper understanding of the mechanisms that underlie neuronal pain processing. The present study reports results of time-resolved measurements of acute heat pain induced changes of the excitatory (Glx) and inhibitory (GABA+) neurotransmitter turnover in the anterior cingulate cortex (ACC) and occipital cortex (OC) by using (1)H MEGA-PRESS spectroscopy. In ACC and OC, the ratio Glx/tCr increased by median values of 21.5% (p < 0.001) and 15.7% (p < 0.001), respectively. At the same time, GABA+/tCr decreased by median values of 15.1% (p = 0.114) in ACC and 12.7% (p < 0.001) in OC. To our knowledge, this study demonstrates for the first time the possibility of quantifying pain-induced neurotransmitter changes in the brain by using functional (1)H MEGA-PRESS. The increase of Glx/tCr may be ascribed to an elevated glutamatergic turnover, while the decrease of GABA+/tCr may reflect reduced activity of the inhibitory system in ACC and OC during pain processing.

Keywords: Acute pain; Anterior cingulate cortex; Functional MRS; GABA; Glu; Glx; MEGA-PRESS; Magnetic resonance spectroscopy; Occipital cortex.