The effects of acupuncture therapy in migraine: An activation likelihood estimation meta-analysis

Acupuncture is an ancient practice that has gained increasing recognition in the treatment of various health conditions, including migraine. This scientific study used an advanced methodology to better understand how acupuncture acts on the brain of people with migraine, analyzing changes in brain activity through functional magnetic resonance imaging.

Migraine represents a significant public health problem, affecting millions of people globally and being one of the leading causes of pain-related disability. According to 2019 epidemiological data, the global prevalence of migraine was approximately 14,000 cases per 100,000 people, with peak occurrence between ages 40 and 44. The economic and social costs are substantial, considering that migraine can significantly reduce productivity at work, school, and in domestic activities. Although there are medications to treat migraine, many have limited efficacy and can cause significant side effects with prolonged use, including dependence and overdose risks.

This makes the development of safe, effective, and well-tolerated treatments such as acupuncture crucial.

The researchers performed a meta-analysis using the activation likelihood estimation method, an advanced statistical technique that allows combining results from multiple neuroimaging studies to identify consistent patterns of brain activity. The aim was to investigate consistent changes in brain regions before and after acupuncture treatment in migraine patients. The team conducted a comprehensive search across eight scientific databases, including PubMed, Embase, and other Chinese databases, covering publications from the inception of these databases until August 2022. Studies that used functional magnetic resonance imaging to assess brain changes in patients diagnosed with migraine according to internationally accepted criteria, treated with manual acupuncture or electroacupuncture, were included.

The methodological quality of the studies was rigorously assessed using checklists specific to functional neuroimaging, and the reporting quality of the interventions was analyzed using the revised standards for reporting interventions in clinical trials of acupuncture.

Fourteen studies met the inclusion criteria, totaling hundreds of migraine patients. The analysis revealed distinct patterns for the immediate and cumulative effects of acupuncture. For immediate effects, observed in five studies that assessed changes shortly after a single acupuncture session, there was mainly decreased activity in frontal regions of the brain, specifically in the superior and middle frontal gyri. These areas are associated with emotional processing and attention, suggesting that acupuncture may have an immediate effect on control of the emotional response to pain.

For cumulative effects, analyzed in eleven studies that assessed changes after multiple treatment sessions, the results were broader and more complex. There was increased activity in several important regions: the thalamus, which is a relay center for sensory information including pain; the insula, crucial for sensory and emotional integration; the superior and middle frontal gyri, related to emotional control and attention; the posterior lobe of the cerebellum, important for coordination and pain processing; the precentral gyrus, involved in motor control; and the anterior cingulate cortex, fundamental in the affective processing of pain.

Simultaneously, cumulative acupuncture treatment resulted in decreased activity in other important brain regions. There was reduced activity in the transverse and superior temporal gyri, areas involved in auditory processing and multisensory integration; in the postcentral gyrus, which corresponds to the primary somatosensory cortex responsible for tactile and pain perception; in the anterior cingulate cortex in a region different from the one that showed an increase; in the parahippocampal gyrus, related to memory and pain perception; in the inferior parietal lobule, important for sensory integration; and in the inferior occipital gyrus, associated with visual processing. These changes suggest that acupuncture acts by modulating multiple brain networks simultaneously.

The results have important clinical implications for both patients and health professionals. For patients, the study provides solid scientific evidence that acupuncture produces measurable and specific changes in the brain, validating reports of symptomatic improvement. The observed changes suggest that acupuncture not only reduces pain perception but also modulates emotional and cognitive aspects associated with migraine, such as anxiety, mood, and concentration. This may explain why many patients report not only pain reduction but also improvement in general well-being, sleep quality, and ability to cope with stress.

For professionals, these findings offer valuable insights into the neurological mechanisms of acupuncture, allowing more targeted and personalized treatments. The evidence that multiple sessions produce broader and more robust effects than isolated sessions supports treatment protocols involving several sessions over time.

The study also revealed interesting differences between the immediate and cumulative effects of acupuncture. While immediate effects mainly showed decreased activity in frontal areas, cumulative effects were characterized by a more complex pattern of increases and decreases in multiple brain networks. This suggests that the neuroplastic mechanisms induced by acupuncture develop and refine over time, with the brain adapting gradually to the treatment. Sensitivity analysis confirmed the robustness of these results, with most identified regions being reproducible even when individual studies were removed from the analysis.

Despite the promising results, the study has some important limitations that should be considered. First, due to limitations of the analytical methodology used, it was not possible to adequately assess publication bias, which is the tendency for studies with positive results to be published more frequently than those with negative results. Second, it was not possible to directly compare brain changes in migraine patients after acupuncture with those of healthy individuals, due to a lack of consistent information on control groups in the included studies. Third, the assessment of intervention reporting quality showed that many aspects of the acupuncture protocols were not adequately described in the original studies, which may limit the reproducibility of the results.

In conclusion, this study provides robust scientific evidence that acupuncture produces specific and measurable changes in brain activity in migraine patients, affecting multiple regions involved in pain, emotion, and cognition processing. The findings suggest that the therapeutic effects of acupuncture are not limited to simple analgesia but involve a complex reorganization of the brain networks responsible