Magnetic Resonance Spectroscopy Assessment of Brain Metabolite Concentrations in Individuals with Chronic Whiplash Associated Disorder: A Cross-sectional Study

Abstract

OBJECTIVES: Pathophysiologic mechanisms underpinning ongoing pain in whiplash associated disorder (WAD) are not well understood, however alterations in brain morphology and function have been observed in this population, as well as in other chronic pain conditions. This study investigated metabolite profiles of brain regions in people with chronic WAD compared with controls. METHODS: Thirty-eight patients with chronic WAD (mean [SD] age 39.5 [11.3] years, 23 female) and 16 pain-free controls (38.9 [12.7] years, 11 female) underwent multi-voxel brain magnetic resonance spectroscopy. At the anterior cingulate cortex (ACC), primary motor cortex (1MC) and somatosensory cortex (SSC), ratios of metabolite concentrations were calculated for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (Ins) and glutamate/glutamine (Glx). Chronic WAD group participants completed clinical questionnaires as well as cold and pressure pain threshold assessment. Data were analysed with hypothesis testing and Spearman correlations (P≥0.05), with Benjamini-Hochberg corrections (5% false discovery rate). RESULTS: No group differences were observed for NAA:Cr, NAA:Cho, Cr:Cho, Glx:NAA, Glx:Cr, Glx:Cho, Ins:NAA, Ins:Cr, Ins:Cho or Ins:Glx for left or right ACC, 1MC or SSC following correction for multiple comparisons. No significant correlations were observed between metabolite ratios and any clinical variable. DISCUSSION: These results suggest that ongoing pain and disability in this population may not be underpinned by metabolite aberrations in the brain regions examined. Further research is required to progress our understanding of cortical contributions to neurophysiologic mechanisms in chronic WAD.