The authors of a paper just published in the journal Pain report that pain from primary dysmenorrhea (PDM) can produce structural changes in the brain that make the subsequent experience of pain worse. The authors note:

“Prolonged nociceptive [painful] input to the central nervous system can induce functional and structural alterations throughout the nervous system. In PDM, a chronic viscero-nociceptive drive of cyclic nature, indications of central sensitization and altered brain metabolism suggest a substantial central reorganization.”

The authors tested their earlier hypothesis that loss of inhibition [calming] of orbitofrontal networks [neural circuits in the frontal areas in the region of the eyes] could result in increased pain and negative feelings with menstrual pain. They used a type of brain MRI called voxel-based morphometry to measure differences in the amount of  gray matter (GM) in subjects with and without PDM. What did their data show?

“Abnormal decreases were found in regions involved in pain transmission, higher level sensory processing, and affected regulation while increases were found in regions involved in pain modulation and in regulation of endocrine function. Moreover, GM changes in regions involved in top-down pain modulation and in generation of negative affect were related to the severity of the experienced PDM pain.”

The most striking and important finding was articulated in their conclusion:

“Our results demonstrate that abnormal GM volume changes are present in PDM patients even in the absence of pain. These changes may underpin a combination of impaired pain inhibition, increased pain facilitation and increased affect. Our findings highlight that longer lasting central changes may occur not only in sustained chronic pain conditions but also in cyclic occurring pain conditions.”

Interestingly, another paper in the same issue of the same journal offers EEG evidence that meditation reduces the negative experience of pain.

“In this study we compared a group of individuals with meditation experience to a control group to test whether any differences in the affective appraisal of pain could be explained by lower anticipatory neural processing.”

The authors used anticipatory and pain-evoked ERP (event related potentials measured by electroencephalography) data and pain unpleasantness reported by test subjects to determine whether experience with meditation made a difference. What did the data show?

“More experienced meditators perceived the pain as less unpleasant relative to controls, with meditation experience correlating inversely with unpleasantness ratings. ERP source data for anticipation showed that in meditators, lower activity in midcingulate cortex relative to controls was related to the lower unpleasantness ratings, and was predicted by lifetime meditation experience.”

Meditators also had less medial prefrontal cortical activity engaged in anticipating pain unpleasantness. The authors concluded:

“Our data is consistent with the hypothesis that meditation reduces the anticipation and negative appraisal of pain…”