Altered amygdalar volume and functional connectivity in primary dysmenorrhoea during the menstrual cycle

Primary dysmenorrhoea (PDM), characterized as menstrual pain without pelvic pathology, is associated with pain-related negative mood and hormone fluctuations. Previous studies strongly supported the link between pain and negative mood in affected individuals; however, it remains largely unknown in patients with PDM.

We focused on the effects how spontaneous pain, negative mood and hormone levels played on the central nervous system in 34 PDM women and 33 matched healthy controls across their cycles (periovulatory phase and menstruation phase) by using T1-weighted and functional imaging. Voxel-based morphometry and functional connectivity (FC) analyses were performed to evaluate brain structural and functional changes. Hormone concentrations (oestradiol, progesterone and cortisol) were also obtained.

Abnormal state-related GM volume in the amygdala was found between periovulatory and menstruation phases in PDM. Furthermore, larger amygdalar volume was observed in patients' menstruation phase, which was significantly correlated with higher levels of cortisol. In addition, we found increased amygdala-seeded FC in vlPFC, which may be associated with pain intensity and negative mood in PDM women during the pain state.

Taken together, we found women with PDM had structural and functional abnormalities in the amygdala, which associated with stress hormone levels, pain intensity and negative mood, may reflect disturbed emotional and pain modulation in women with PDM.

Our findings provide further evidence of amygdala-related abnormalities, which may be associated with pain-related affective distress and hormonal fluctuations in women with PDM, and complement the brain mechanism investigations for the pathophysiology of PDM.