Progress of Acupuncture Therapy in Diseases Based on Magnetic Resonance Image Studies: A Literature Review

Acupuncture is a millennia-old therapeutic practice from traditional Chinese medicine that has been gaining growing worldwide acceptance because of its demonstrated beneficial effects in various health conditions. Although clinical studies have proven its efficacy in the treatment of depression, ischemic stroke, migraine, functional diarrhea, and Alzheimer disease, the brain mechanisms responsible for the therapeutic effects of acupuncture are still not completely understood. This knowledge gap has generated skepticism in the scientific community and has limited broader acceptance of this therapeutic modality. In recent decades, functional magnetic resonance imaging has emerged as a valuable tool for investigating how acupuncture influences brain function, offering a unique opportunity to unravel the mysteries behind this ancient medical practice.

This study aimed primarily to provide a comprehensive and updated review of the scientific literature on the effects of acupuncture on the brain, using functional magnetic resonance imaging studies in patients with different clinical conditions. The researchers carried out a systematic search in four major scientific databases — PubMed, Embase, Web of Science, and Cochrane Library — from the start of publications through January 2021. Only original studies published in English that used true acupuncture, electroacupuncture, or laser acupuncture in patients with specific diseases were included, excluding studies involving only healthy volunteers. The rigorous methodology resulted in the selection of 107 studies that met the inclusion criteria, involving a total of 2,957 patients and 928 healthy controls.

The results revealed interesting patterns about the current state of acupuncture neuroimaging research. Stroke was the most studied condition, representing the largest proportion of analyzed works, followed by other neurologic and digestive conditions. The acupoint GB-34 (Yanglingquan), located on the lateral leg, emerged as the most frequently used, especially for treatment of stroke and Parkinson disease. This point, according to traditional Chinese medicine theory, is considered the meeting point of the gallbladder meridian and the influential point of the tendons, traditionally used to treat motor system disorders.

The studies showed that stimulation of GB-34 mainly activates brain regions related to movement, including the premotor cortex, supplementary motor area, and supramarginal gyrus. In methodologic terms, resting-state functional magnetic resonance imaging and functional connectivity analysis were the most used approaches, representing a growing trend in recent years of research.

The clinical implications of these findings are significant for both patients and health care professionals. The study demonstrated that the effects of acupuncture on the brain differ substantially between patients with pathologic conditions and healthy individuals, suggesting that acupuncture has a therapeutic specificity that is manifested primarily in states of imbalance or disease. In patients, the brain activation induced by acupuncture predominantly occurs in regions related to the specific condition being treated, supporting the traditional Chinese medicine theory that acupuncture acts by restoring the body's internal balance. The researchers also identified several factors that influence the efficacy of acupuncture, including depth of needle insertion, the sensation of de qi (the specific sensation obtained during acupuncture), the number and location of points used, and psychological factors such as patient expectation.

Particularly important was the finding that deep acupuncture was more effective than superficial acupuncture for certain conditions, and that the combination of multiple acupuncture points activated more extensive brain regions than single points.

The study also addressed the controversial issue of placebo acupuncture, revealing that the type of placebo control used significantly affects results. The researchers identified three main types of placebo control: cutaneous stimulation at the same points, use of blunt needles that do not penetrate the skin, and insertion of needles at non-acupuncture points. Each type produced different patterns of brain activation, highlighting the importance of properly choosing the control group in acupuncture studies. This finding has important implications for the design of future clinical studies and for the interpretation of results from prior research.

Despite the promising findings, the study acknowledges several important limitations that must be considered in interpreting the results. The small sample size in most analyzed studies limits the generalizability of the findings, while significant heterogeneity in experimental designs and analytical methods makes direct comparisons across studies difficult. Standardization of magnetic resonance imaging parameters and acupuncture protocols is still inconsistent, contributing to the variability of results. In addition, most studies focused on the immediate effects of acupuncture, with few investigating the effects of prolonged treatments that are more representative of real clinical practice.

The authors also note that nonspecific factors, such as the psychological attitude of participants toward acupuncture and the type of disease studied, may significantly interfere with observed brain responses.

To advance this field of research, the authors recommend that future studies use larger samples, more careful experimental designs, and multimodal neuroimaging techniques. Standardization of acupuncture methods and magnetic resonance imaging parameters is essential to increase homogeneity of results and allow more reliable comparisons across studies. It is also necessary to develop studies that investigate the effects of long-term acupuncture treatments, which are more relevant to clinical practice. The incorporation of machine learning and artificial intelligence techniques may eventually allow personalized prediction of acupuncture efficacy based on individual brain activation patterns.

This work represents an important step toward establishing a solid scientific basis for acupuncture, potentially leading to greater acceptance of this therapeutic modality in modern medicine and contributing to the development of more effective and personalized treatments for various health conditions.