Menstrual cramps may alter brain structure.

From ScienceDaily:

Primary dysmenorrhea (PDM), or menstrual cramps, is the most common gynecological disorder in women of childbearing age. Lower abdominal pain starts with the onset of menstrual flow and this ongoing pain stimulus can cause alterations throughout the nervous system.

In a study scheduled for publication in the September issue of the journal Pain, researchers report abnormal changes in the structure of the brain in PDM patients, whether or not they are in fact experiencing pain.

Lead investigator, Professor Jen-Chuen Hsieh, MD, PhD, Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan, commented, "Our results demonstrated that abnormal GM [gray matter] changes were present in PDM patients even in absence of pain. This shows that not only sustained pain but also cyclic occurring menstrual pain can result in longer-lasting central changes. Although the functional consequences remain to be established, these results indicate that the adolescent brain is vulnerable to menstrual pain. Longitudinal studies are needed to probe hormonal interaction, fast-changing adaptation (intra-menstrual cycle) and whether such changes are reversible or not."