A recent study sheds light on the question of how acupuncture helps people with chronic pain and whether it’s more than a placebo effect. Acupuncture may achieve its long-term pain relief by remapping nervous system signals in the brain, according to findings from a sham-controlled acupuncture investigation of carpal tunnel syndrome (CTS). Researchers at Massachusetts General Hospital in Boston, Massachusetts, chose CTS to study the underlying mechanisms for acupuncture’s effectiveness, because CTS is a pain disorder with established biomarkers and measurable treatment outcomes. Principal researcher, Vitaly Napadow, PhD, director, Center for Integrative Pain Neuroimaging at MGH, has conducted studies that demonstrate that in CTS, parts of the brain that typically receive signals related to touch are remapped, particularly in the primary somatosensory cortex—a biomarker of CTS. And, brain cells that usually respond to touch signals from specific fingers respond to signals from multiple fingers.
Researchers reached their conclusion that acupuncture remaps nervous system signals in the brain after analyzing data from a comparison of functional magnetic resonance imaging [MRI] taken before and after therapy among three different groups of CTS patients. The subjects either received authentic acupuncture at the affected hand, authentic acupuncture at the opposite ankle, or sham acupuncture at the affected hand. Interestingly, all three group members reported symptom relief. However, only real acupuncture at the affected hand both reduced pain and altered brain signaling patterns and was associated with long-term symptom improvement.
Investigators proposed a theory for why sham acupuncture provides short-term benefits. “Sham acupuncture may ‘work’ by modulating known placebo circuitry in the brain,” said Napadow in a Massachusetts General Hospital news release. “In contrast, real acupuncture may improve CTS symptoms by rewiring the primary somatosensory cortex, in addition to modulating local blood flow to the peripheral nerve in the wrist. In other words, both peripheral and central neurophysiological changes in CTS may be halted or even reversed by electro-acupuncture interventions that provide more prolonged and regulated input to the brain—something that future, longer-term neuroimaging studies should explore.”
The study is published in the journal Brain (2017; doi: 10.1093/brain/awx015).