Altered Cortical Structure in Primary Dysmenorrhea: Cortical Thickness Mediates the Association Between Estradiol and...

Primary dysmenorrhea (PDM), as a form of chronic pelvic pain, has a complex pathophysiology involving hormonal factors, central nervous system alterations, and maladaptive pain cognition. Previous neuroimaging studies have demonstrated structural brain alterations in patients with PDM. However, the relationships among hormone levels, brain structural changes, and pain catastrophizing remain poorly understood. This study aimed to investigate brain structural alterations and their associations with estradiol (E₂) levels and pain catastrophizing in patients with PDM.

T1-weighted MRI scans and E₂ sampling were acquired during the menstrual phase from 45 patients with PDM and 44 age-matched healthy controls. Cortical thickness, volume, and folding were compared using a general linear model. Among the regions showing significant group differences, mediation analyses focused specifically on the right postcentral gyrus to examine whether its cortical thickness mediated the relationship between E₂ levels and Pain Catastrophizing Scale (PCS) magnification scores in patients with PDM. The McGill Pain Questionnaire (MPQ) was used to measure the quality and intensity of menstrual pain.

The PDM group scored significantly higher on the MPQ and PCS, suggesting greater pain perception and psychologic distress. Patients with PDM exhibited alterations in cortical thickness, volume, and folding within specific brain regions. Notably, the cingulate cortex, orbitofrontal cortex, and postcentral gyrus demonstrated substantial changes. Mediation analysis revealed that E₂ levels were positively correlated with PCS magnification scores (r = 0.342, p = 0.023), and this relationship was fully mediated by cortical thickness of the right postcentral gyrus (indirect effect = 0.045, p < 0.001).

This study identified brain structural alterations during the menstrual phase in patients with PDM and further found that cortical thickness of the right postcentral gyrus mediated the relationship between estradiol levels and pain magnification. These findings provide new insights into the complex mechanisms underlying PDM.