Researchers Show Brain Differences in 2 Different Types of Menstrual Migraine

In a study published in Scientific Reports, researchers highlighted structural and functional brain differences among those who suffer menstrual-related migraine (MRM) and pure menstrual migraine (PMM).

The International Classification of Headache Disorders III beta notes menstrual migraines (MM) are associated with the menses and MM is divided into 2 subcategories: MRM and PMM. “Unlike PMM, MRM involves migraine attacks that occur outside of the menstrual cycle,” authors wrote, while “an epidemiological survey showed that 21% of women with migraine experience MM, and approximately 66% experience MRM.”

It is generally accepted that an inflammatory response may be a possible mechanism for the pathogenesis of MM. However, differences in attack frequency may mean PMM and MRM have different effects on the brain’s structure and function.

Researchers used resting-state functional MRI (rsfMRI) and structural magnetic resonance imaging (sMRI) to evaluate differences between 32 patients with MRM and 16 patients with PMM. All patients were recruited between June 2015 and August 2018.

Of those with MRM, mean (SD) age was 33.41 (6.23) years, while mean age of those with PMM was 31.75 (7.85) years. All patients stopped prophylactic medications for migraine 4 weeks before the examination and did not experience a typical migraine attack for at least 1 week prior to the MRI.

Although no differences in migraine duration or intensity were reported between the 2 cohorts, those with MRM exhibited a significantly higher migraine frequency compared with those with PMM (P <.001). Patients also did not exhibit differences in grey matter volume.

Investigators applied voxel-based morphometry (VBM) on sMRI, and both the amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) in rsfMRI were calculated. ALFF demonstrates the intensity of regional spontaneous neural activity while ReHo can demonstrate neural concordance.

Researchers found:

• MRM patients exhibited lower ALFF values at the dorsolateral prefrontal cortex (DLPFC) and medial prefrontal cortex (mPFC) than PMM patients
• The MRM group showed significantly higher ReHo values in the DLPFC
• Higher values in the mPFC were related to higher expression of calcitonin gene-associated peptide (CGRP) in the PMM group (r = 0.5, P = .048)
• Combined ALFF and ReHo analyses revealed significantly different spontaneous neural activity in the DLPFC and mPFC, between MRM and PMM patients
• ALFF values in the mPFC were positively correlated with CGRP expression in the PMM group

The DLPFC and mPFC pertain to the frontal cortex, one of the more prominent regions associated with brain activity in migraineurs, researchers explained. Because of this, “we speculate the lower level of regional functional neural activity in the DLPFC and mPFC of MRM patients may influence the inhibitory control of pain perception and mediation of additional attacks of migraine outside of the menstrual cycle,” authors wrote.

A relatively small sample size, lack of hormonal testing, and absence of a healthy control group mark limitations to the study. Future longitudinal fMRI studies ought to be carried out to establish and confirm the current findings, researchers concluded.

Reference

Xu T, Zhang Y, Wang C. Brain structural and functional differences between pure menstrual migraine and menstrually-related migraine. Sci Rep. Published online October 5, 2020. doi: 10.1038/s41598-020-73399-0