Pressure Pain Sensitivity and Insular Combined Glutamate and Glutamine (Glx) Are Associated with Subsequent Clinical Response to Sham But Not Traditional Acupuncture in Patients Who Have Chronic Pain.

Abstract

Clinical trials of acupuncture in chronic pain have largely failed to demonstrate efficacy of traditional over sham acupuncture. However, it should be noted that sham acupuncture is not inert. To determine if experimental-pressure pain assessment and chemical neuroimaging can identify differential responsiveness to sham as opposed to traditional acupuncture. Fifty patients with fibromyalgia were randomized to either 9 traditional (TA) or sham (SA) acupuncture treatments over a period of 4 weeks. Both participants and assessors were blinded. The main outcome measures were pressure-pain sensitivity at the thumbnail, insular glutamate+glutamine (Glx), and clinical pain. PATIENTS WITH LOW PAIN SENSITIVITY (LPS), BUT NOT WITH HIGH PAIN SENSITIVITY (HPS), HAD A SIGNIFICANTLY REDUCED CLINICAL PAIN RESPONSE TO SA (CHANGE IN MEAN [STANDARD DEVIATION (SD)]: HPS -8.65 [7.91]; LPS -2.14 [6.68]; p=0.03). This relationship was not the case for TA (HPS -6.90 [4.51]; LPS -6.41 [9.25]; p=0.88). SA-treated patients who were more sensitive also had greater baseline levels of insular Glx than patients who were less sensitive (Glx mean [SD]: HPS 11.3 [1.18]; LPS 10.2 [0.54]; p=0.04). Pressure-pain testing may identify patients who are less likely to respond to SA. This effect may relate to the levels of brain excitatory neurotransmitters.