Revealing the Central Mechanism of Acupuncture for Primary Dysmenorrhea Based on Neuroimaging: A Narrative Review.

Objective: The central mechanism of acupuncture for primary dysmenorrhea was explored by summarizing the changes in different regional networks of the brain induced by acupuncture stimulation by analyzing the existing studies. Methods: The original studies were collected and selected from three English databases such as PubMed and four Chinese databases as China Knowledge Network (CNKI). The main keyword clusters are neuroimaging, acupuncture, and primary dysmenorrhea. Results: The literature review yielded 130 possibly qualified studies, and 23 articles fulfilled the criteria for inclusion. Regarding the type of acupuncture studies, 6 moxibustion studies and 17 manual acupuncture studies for primary dysmenorrhea were included. Based on functional magnetic resonance imaging (fMRI), perfusion-weighted imaging (PWI), and positron emission tomography-computer tomography techniques (PET-CT), one or more analysis methods such as amplitude of low-frequency fluctuations (ALFF), regional homogeneity (ReHo), functional connectivity (FC), and independent components analysis (ICA) were used. The results are summarized. To summarize the high-frequency brain area alterations observed in patients with acupuncture-induced primary dysmenorrhea were the anterior cingulate gyrus, thalamus, insula, precentral gyrus, middle frontal gyrus, postcentral gyrus, putamen, and cerebellum. Conclusion: The results suggest that the mechanism of acupuncture in the treatment of primary dysmenorrhea is the involvement of networks regulating different areas of the brain in the analgesic effects of acupuncture. The brain regions involved in primary dysmenorrhea acupuncture analgesia were mainly located in the pain matrix, default mode network, salience network, and limbic system.

[Effect of acupuncture on brain functional connectivity strength in patients with primary dysmenorrhea].

OBJECTIVE: To investigate the effect of acupuncture on the brain functional activities of the patients with primary dysmenorrhea based on the resting-state functional magnetic resonance imaging (rs-fMRI), and to provide visual evidence for the central mechanism of acupuncture in treatment of primary dysmenorrhea. METHODS: Forty-two patients of primary dysmenorrhea were enrolled and randomly divided into an observation group (21 cases, 1 case dropped off) and a control group (21 cases, 2 cases dropped off, 3 cases withdrawal). In the observation group, acupuncture was exerted at Sanyinjiao (SP 6) and Guanyuan (CV 4), started 5-7 days before menstrual flow, once a day till menstrual onset, for a total of 3 menstrual cycles. No intervention was applied in the control group. The scores of visual analogue scale (VAS) and Cox menstrual symptom scale (CMSS) were observed in both groups before and after treatment. Based on rs-fMRI, the data of resting-state functional magnetic resonance were collected from two groups before and after treatment. Combined with functional connectivity strength (FCS) and functional connectivity (FC) analysis, the differences of brain regions before and after treatment were compared between the two groups and the correlation was analyzed between their functional connectivity changes and the improvements in VAS and CMSS scores of the patients in the observation group. RESULTS: In the observation group, the scores of VAS and CMSS were all decreased after treatment (P<0.05), while the scores related to the symptom time in CMSS was reduced in comparison with that before treatment in the control group (P<0.05). The score reducing ranges of VAS and CMSS in the observation group were larger than the control group (P<0.05). Compared before treatment, FCS of the right middle cingulate cortex and the left cuneus was increased, while FCS of the left inferior parietal lobule was decreased after treatment in the observation group. In the control group, FCS of the left orbital frontal cortex was increased after treatment. Compared with the control group, FCS of the left anterior insula was increased in the observation group after treatment. FC analysis was performed using the left anterior insula as the seed point. In comparison with the control group, FC of the left anterior insula was increased either with the inferior temporal gyrus or with the right hippocampus; and was decreased either with the middle occipital lobe or with the right dorsolateral prefrontal cortex in the observation group after treatment. In the observation group, FC between the left anterior insula and the right hippocampus was positively correlated with the improvements in symptom severity (r =0.385, P<0.05) and symptom time (r =0.510, P<0.05) of CMSS, and FC between the right dorsolateral prefrontal cortex and the left anterior insula was negatively correlated with the improvement in symptom severity of CMSS after treatment (r =-0.373, P<0.05). CONCLUSION: The anterior insula may be the key brain region in treatment of primary dysmenorrhea with acupuncture. Acupuncture may relieve dysmenorrhea and the related symptoms through strengthening the functional connectivity of anterior insula-limbic system and anterior insula-control network.

Abnormal white matter microstructure along the thalamus fiber pathways in women with primary dysmenorrhea.

Primary dysmenorrhea (PDM) is a cyclic menstrual pain in the absence of pelvic anomalies, and women with PDM have an increased sensitivity to pain than the internal and external areas associated with menstrual pain. However, the brain abnormality in the ascending pain pathways in dysmenorrhea remains largely unclear. As the thalamus plays a significant role in transmission of nociceptive input, we examined whether white matter microstructure of the thalamus-related fiber tracts obtained by DTI in women with PDM (n = 47) differs from healthy controls. A novel tractography atlas-based analysis method that detects tract integrity and altered microstructural properties along selected fibers was employed. The fiber bundles of interest contained the thalamus- primary somatosensory cortex (SI), thalamus- dorsal anterior cingulate cortex (dACC)/supplementary motor area (SMA), thalamus-insula, and thalamus-ACC. As compared with controls, abnormal white matter microstructures were found along the thalamus-related white matter fiber tracts. Additionally, the intensity of menstrual pain was significantly associated with diffusion measures of thalamus-SI fiber connections. Our study suggested that the thalamus-related pain processing pathways had altered white matter integrity that persisted beyond the time of menstruation, and the white matter microstructure of the thalamus-SI pathways was closely related to menstrual pain in the intensity by women with PDM.

Evaluation of the efficacy of Fructus agni casti in women with severe primary dysmenorrhea: a prospective comparative Doppler study.

AIM: The aim of this case-control study was to compare the efficacy of ethinyl estradiol/drospirenone and Fructus agni casti in women with severe primary dysmenorrhea measuring uterine artery blood flow via Doppler ultrasonography. METHODS: A total of 60 women with severe primary dysmenorrhea and 30 healthy women (control) were included in this study. Thirty patients were treated with ethinyl estradiol 0.03 mg/drospirenone (group 1) and another 30 were treated with Fructus agni casti (group 2) during three menstrual cycles. Before and at the end of third month of therapy visual analog scale (VAS) scores, pulsatility index (PI), resistance index (RI) of uterine artery were recorded before and after receiving therapy on the first day of the menstrual cycle. RESULTS: Mean PI and RI values in patients with severe primary dysmenorrhea were significantly higher than in the control groups on the first day of the menstrual cycle (P < 0.0001). Mean PI and RI values were significantly lower after the treatment in both groups compared to before values (P < 0.001 for both). After using the drugs for three menstrual cycles, VAS scores were significantly dropped in both groups compared to before treatment values (P < 0.0001 for both); however, there were no significant differences in terms of Doppler findings between group 1 and 2. CONCLUSION: The effectiveness of Fructus agni casti was similar to that of ethinyl estradiol/drospirenone in patients with primary dysmenorrhea.