Abnormal white matter integrity during pain-free periovulation is associated with pain intensity in primary dysmenorrhea.

Neuroimaging studies have preliminarily described brain structural and functional differences that consist of the pain transmission and modulation systems in primary dysmenorrhea (PDM). However, whether PDM subjects have distinctive white matter (WM) alteration during the time when there is no painful menstruation is largely unknown. If that is the case, whether such specific variability is interconnected with the dysmenorrhic symptoms is unclear. In the current study, diffusion tensor imaging (DTI) was performed on 24 PDM females and 24 healthy control subjects. Optimized tract-based spatial statistics was employed to examine the between group differences in DTI measures including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). Visual analogue scale (VAS) was used to rate the intensity of the abdominal pain at periovulation and menstruation. In our results, PDM had lower FA coupled with higher MD and RD in widespread WM fibers including the splenium part of the corpus callosum, the posterior limb of the internal capsule, the anterior, superior and posterior corona radiata, and the posterior thalamic radiation (P < 0.05, FWE corrected). Further correlation analyses revealed close correlations between these DTI measures and VAS of the menstrual phase when the PDM showed serious abdominal pain. In the current study, we found PDM females had abnormal WM integrity involving pain transmission and modulation systems when they were at periovulation. Additionally, these WM abnormalities may closely associate with the intensity of painful menstruation. These observations complement the brain microstructural investigations for the pathophysiology of PDM.