Until recently, the predominant pathology of chronic
pelvic pain conditions was thought to reside in the peripheral tissues. However, mounting evidence from neuroimaging studies suggests an important role of the central nervous system in the pathogenesis of these conditions. In the present cross-sectional study,
proton magnetic resonance spectroscopy (1H-MRS) of the brain was conducted in female patients with urologic chronic
pelvic pain syndrome (UCPPS) to determine if they exhibit abnormal concentrations of brain metabolites (e.g. those indicative of heightened excitatory tone) in regions involved in the processing and modulation of
pain, including the anterior cingulate cortex (ACC) and the anterior and posterior insular cortices. Compared to a group of age-matched healthy subjects, there were significantly higher levels of
choline (p = 0.006, uncorrected) in the ACC of UCPPS patients. ACC
choline levels were therefore compared with the region's resting functional connectivity to the rest of the brain. Higher
choline was associated with greater ACC-to-limbic system connectivity in UCPPS patients, contrasted with lower connectivity in controls (i.e. an interaction). In patients, ACC
choline levels were also positively correlated with negative mood. ACC γ-
aminobutyric acid (
GABA) levels were lower in UCPPS patients compared with controls (p = 0.02, uncorrected), but this did not meet statistical correction for the 4 separate regional comparisons of metabolites. These results are the first to uncover abnormal
GABA and
choline levels in the brain of UCPPS patients compared to controls. Low
GABA levels have been identified in other
pain syndromes and might contribute to CNS hyper-excitability in these conditions. The relationships between increased ACC
choline levels, ACC-to-limbic connectivity, and negative mood in UCPPS patients suggest that this metabolite could be related to the affective symptomatology of this syndrome.