Acupuncture for radicular pain: a review of analgesic mechanism

Radicular pain represents one of the most challenging types of neuropathic pain in medical practice, characterized by intense pain, numbness, and tingling that radiate along specific nerve pathways. This condition can result from disc herniation, spinal stenosis, or vertebral degeneration, significantly affecting patients' quality of life. Despite advances in modern medicine, the treatment of radicular pain remains complex, with important limitations in both surgical and pharmacologic approaches. In this context, acupuncture emerges as a promising therapeutic alternative, grounded in thousands of years of clinical practice in traditional Chinese medicine.

The main objective of this review was to examine and synthesize the current scientific knowledge on the mechanisms by which acupuncture produces pain relief in patients with radicular pain. The researchers conducted a comprehensive analysis of the scientific literature, including clinical and experimental studies that investigated the effects of acupuncture on different types of radicular pain, including lumbar radiculopathy, cervical radiculopathy, and radicular pain related to spinal stenosis. The methodology involved critical review of research that used both manual acupuncture and electroacupuncture, analyzing everything from studies in animal models to clinical trials in humans.

The results revealed that acupuncture acts through multiple biological mechanisms to promote relief of radicular pain. At the peripheral level, acupuncture demonstrated the ability to reduce muscle spasms and decrease mechanical pressure on nerve roots while simultaneously improving local microcirculation. This effect is particularly relevant because nerve root compression is one of the main causes of radicular pain. In addition, acupuncture has been shown to reduce local edema and improve oxygen delivery to tissues, contributing to the reduction of nerve compression symptoms.

At the molecular level, the research identified that acupuncture modulates important inflammatory signaling pathways, specifically inhibiting the HMGB1/RAGE and TLR4/NF-κB pathways. These pathways are crucial in the production of pro-inflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α, which contribute significantly to peripheral sensitization and the perpetuation of pain. The ability of acupuncture to reduce the release of these inflammatory substances represents a fundamental mechanism for its analgesic effects.

In the central nervous system, the findings demonstrated that acupuncture influences synaptic plasticity in the spinal cord, modulating important synaptic proteins such as PSD-95 and GAP-43, as well as affecting neurotrophic factors such as BDNF. This modulation of synaptic plasticity is essential for interrupting the cycles of central sensitization that maintain chronic pain. Functional neuroimaging studies revealed that acupuncture also acts on specific brain regions involved in pain processing, including the medial prefrontal cortex, anterior cingulate cortex, and thalamus, components of the brain's default mode network. These findings provide solid neurobiological evidence for the analgesic effects of acupuncture, demonstrating that its benefits extend from the periphery to the higher centers of pain processing.

The clinical implications of these findings are substantial for both patients and health care professionals. For patients suffering from radicular pain, acupuncture offers a safe and effective therapeutic option, with a low incidence of adverse effects compared with conventional medications or surgical interventions. Research has demonstrated that acupuncture can provide significant pain relief, particularly when integrated into multidisciplinary approaches that include physical therapy and other conservative modalities. For health care professionals, these results provide a robust scientific basis for incorporating acupuncture into treatment protocols for radicular pain, especially considering that many patients prefer to avoid analgesic medications because of side effects or have contraindications to surgery.

It is important to acknowledge the limitations of this review and the considerations that should guide future research. Although the studies demonstrate significant correlations between acupuncture treatment and symptom improvement, establishing definitive causal relationships remains challenging because of the complex, multifactorial nature of the pain experience. Standardization of acupuncture protocols remains an obstacle, given that point selection, insertion depth, and treatment duration can vary significantly among practitioners and patients. In addition, many studies presented relatively small sample sizes, limiting the generalizability of results.

The need for larger randomized controlled trials, with more diverse populations and objective measures of pain and function, remains critical to advancing our understanding of the mechanisms of acupuncture.

Acupuncture represents a valuable therapeutic modality for the management of radicular pain, acting through well-defined biological mechanisms that span from modulation of peripheral inflammation to changes in brain function. Although more research is needed to fully elucidate all aspects of its analgesic action, current evidence supports its integration into comprehensive treatment strategies for radicular pain, offering hope for patients seeking safe and effective alternatives to conventional treatments.