The low-frequency BOLD signal oscillation response in the insular associated to immediate analgesia of ankle acupuncture in patients with chronic low back pain

PURPOSE: The present study evaluated the modulation effect of a painless acupuncture technique, ankle acupuncture (AA), on resting-state functional change in patients with chronic low back pain (CLBP). PATIENTS AND METHODS: Fourteen participants diagnosed with CLBP received AA and underwent one brain functional image scan after tactile stimulation and another one following the insertion of the needle. The needling sensations and clinical pain intensities were evaluated after the end of each functional image scan. The significance levels of Visual Analog Scales/Scores (VASs) before and after acupuncture were determined using paired t-test. The brain areas showing differences in the amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) between the two scans were identified. We also explored the relationship between mean ALFF values in brain areas identified and VAS scores based on Pearson correlation coefficient. RESULTS: A complete-case analysis was performed on 12 participants. Neither different needling sensations nor any local sensations during the two scans was found. The clinical findings indicated that the scores of VAS scores were significantly lower after AA intervention (P<0.001). Compared with those after tactile stimulation, ALFF decreased in the left insular and increased in the left precuneus and right precentral gyrus, and fALFF decreased in the left insular, during retaining of AA (corrected). Moreover, there was a positive correlation found between mean ALFF change in the left insular and that of VAS values (P<0.05). CONCLUSION: The present study demonstrated the low-frequency BOLD signal oscillation response in the left insular in brain activity was associated with an immediate analgesia of AA in patients with CLBP, which provides new insights into intrinsic connections between low-frequency brain signals and analgesic effects of acupuncture.