Neuroimaging Studies of Acupuncture on Low Back Pain: A Systematic Review

Acupuncture, a millennia-old practice from traditional Chinese medicine, has been widely used in the treatment of chronic low back pain. This condition affects approximately 40% of people during their lifetime and is considered one of the leading causes of disability worldwide. Although several studies confirm the efficacy of acupuncture for low back pain relief, the neurologic mechanisms by which it acts on the brain had not been fully clarified. For this reason, researchers have been using advanced neuroimaging techniques, such as functional magnetic resonance imaging, to investigate how acupuncture modifies brain activity in patients with low back pain.

This study represents a comprehensive systematic review that analyzed 19 studies published between 2007 and 2020, involving 613 patients with low back pain and 120 healthy individuals as a control group. The researchers conducted searches in seven scientific databases, including studies in both English and Chinese, to ensure a complete view of the available literature on the topic. The methodology included a rigorous analysis of study quality and extraction of data on participant characteristics, types of acupuncture intervention, and neuroimaging results.

The results revealed interesting patterns about how acupuncture is studied in clinical practice. The vast majority of studies (78.9%) used manual acupuncture, while the rest used electroacupuncture. About 89.5% of the research focused on functional brain changes caused by acupuncture, and 68.4% used resting-state functional magnetic resonance imaging. The study identified that patients with low back pain show specific alterations in important brain regions, including the prefrontal cortex, insula, cerebellum, primary somatosensory cortex, and anterior cingulate cortex.

These areas are closely related to processing of pain, emotion, and cognition.

The most significant findings showed that acupuncture produces brain changes in regions fundamental to pain control. The prefrontal cortex and insula were the areas most frequently modified by treatment, followed by the cerebellum, primary somatosensory cortex, and anterior cingulate cortex. These regions are part of the so-called 'pain matrix,' a neural network responsible for processing painful sensations. In addition, acupuncture also influenced other important neural networks, including the default mode network (related to the brain's resting state), the salience network (which processes relevant information), and the descending pain modulation system (which controls the intensity of perceived pain).

Some studies demonstrated significant correlations between clinical improvements of patients and the changes observed on brain imaging, suggesting that the neurologic changes are directly related to pain relief.

For patients and health care professionals, these findings offer robust scientific evidence on how acupuncture works in the treatment of low back pain. The study demonstrates that acupuncture not only relieves symptoms superficially but actually modifies the activity of brain circuits fundamental to pain processing. This may help explain why many patients experience lasting relief with acupuncture treatment. For professionals, this information can guide the selection of acupuncture points and more effective treatment strategies.

The research also suggests that both manual acupuncture and electroacupuncture are capable of producing beneficial brain alterations, although they may act through slightly different mechanisms.

Despite the promising findings, the study has some important limitations that must be considered. The main limitation was the great variability in the methodologies used by the different analyzed studies, including different types of acupuncture, points of application, treatment duration, and neuroimaging techniques employed. This heterogeneity made it impossible to perform a quantitative meta-analysis of the results, limiting the ability to draw definitive conclusions. In addition, many studies included relatively small samples of patients, and some presented risks of methodologic bias.

Most research focused only on functional effects on the brain, with few studies investigating long-term structural changes. The authors also noted that almost all research used only magnetic resonance imaging, suggesting that future studies could benefit from the combination of multiple neuroimaging techniques for a more complete understanding of the mechanisms of action of acupuncture. Despite these limitations, the review provides valuable evidence that acupuncture promotes beneficial changes in the brain of patients with low back pain, offering a solid scientific basis for its clinical use and directing future research in the area.