Immediate Modulations of Cheek Acupuncture on Brain Oscillations and Connectivity in Individuals with Chronic Pain

Chronic pain challenges global healthcare due to its complexity and the limitations of current treatments. Cheek acupuncture (CA), which targets specific acupoints on the cheek based on the biological holographic model, has shown promise for immediate pain relief. Despite its efficacy across various clinical studies, the mechanisms underlying its analgesic effects remain unclear. In this study, through resting electroencephalography analysis of 37 participants with chronic pain before, during, and after CA therapy, we investigated the electrophysiological modulations underlying the immediate analgesic effects of CA, with further comparison to an additional 13 participants with chronic pain undergoing sham acupuncture to exclude the potential placebo effects. Compared with sham acupuncture, CA demonstrated a significant immediate analgesic effect for chronic pain. Meanwhile, CA also triggered significant modulations on brain oscillations and their synchrony, which are distinct at different acupuncture procedures. Specifically, needle insertion of CA significantly reduced theta oscillations and enhanced gamma oscillations, suggesting a downregulation of hyperactive thalamic activity and an improvement of feedforward communication in pain processing; while after needle withdrawal, beta-band synchrony within the frontal lobe was decreased, indicating an improvement in the efficiency of feedback regulatory information transmission by reducing excessive connections. These modulations together improve the integration of nociceptive and contextual information in pain processing. Notably, the reduced theta oscillations were significantly correlated with the magnitude of pain relief and exerted a weak mediating effect in analgesia. Our findings provide electrophysiological insights into the immediate analgesic mechanism of CA.