Quantitative 3.0T MR spectroscopy reveals decreased creatine concentration in the dorsolateral prefrontal cortex of patients with social anxiety disorder

Abstract

Background: The brain biochemical changes of social anxiety have not been clarified although there have been a limited number of MR spectroscopic studies which utilized metabolite/creatine ratios. Present study aimed to explore the alteration of absolute metabolite concentration in social anxiety disorder using quantitative MR spectroscopy.

Materials and methods: With a 3.0T MR scanner, single voxel MR spectroscopy (stimulated echo acquisition mode, TR/TE/TM = 2000/20/16 ms) was performed in the left dorsolateral prefrontal cortex and related regions of nine medication-free patients with social anxiety disorder and nine controls. Absolute metabolite concentration was calculated using tissue water as the internal reference and corrected for the partial volume of cerebrospinal fluid.

Results: In the left dorsolateral prefrontal cortex, the N-acetyl aspartate/creatine ratio of patients was significantly higher than that of controls, and this was due to the decrease of creatine concentration instead of the increase of N-acetyl aspartate concentration. Furthermore, the creatine concentration of the left dorsolateral prefrontal cortex was negatively correlated with the scores of Liebowitz social anxiety scale.

Conclusions: The alteration of creatine level in the left dorsolateral prefrontal cortex suggests abnormal energy metabolism and correlates with symptom severity in social anxiety disorder. And metabolite concentration is preferable to metabolite/creatine ratio for the investigation of individual, absolute metabolite changes in this region of social anxiety disorder.

Figure 1. MRS data acquisition and post-processing.

(a) and (b) are the transversal and sagittal view of the brain, respectively. The red rectangles indicate the volume of interest representing the left dorsolateral prefrontal cortex (DLPFC) from where the spectrum (c) is acquired. (c) is the spectrum of the left DLPFC. From bottom to the top are the original spectrum, the estimated spectrum yielded by ‘Advanced Method for Accurate, Robust and Efficient Spectral fitting (AMARES)’ package, the individual peak components and the residual spectrum.

Figure 2. Correlation between creatine concentration and LSAS score.

Creatine concentration of the left DLPFC is negatively correlated with the avoidance part of the LSAS score (r = −0.589, p = 0.010) (a), the fear part of the LSAS score (r = −0.553, p = 0.017) (b), and the total LSAS score (r = −0.594, p = 0.007) (c), respectively.