Cerebral blood flow effects of pain and acupuncture: a preliminary single-photon emission computed tomography imaging study.

BACKGROUND The purpose of this study was to investigate the cerebral blood flow changes associated with the analgesic effect of acupuncture in patients with chronic pain. METHODS Seven patients presenting with a chronic pain syndrome and 5 healthy controls were included. All single-photon emission computed tomography (SPECT) scans were acquired with a uniform protocol. The patient group was injected with the radioisotope hexamethyl propyleneamine oxime (HMPAO) while experiencing their usual level of pain. A baseline scan was acquired approximately 20 minutes after administration of the HMPAO. The patient then underwent acupuncture therapy with needles placed in points specifically selected to relieve pain. When the pain improved, as determined by a 10-digit score for pain assessment, the patient was reinjected with HMPAO and imaged 20 minutes later for the acupuncture scan. The reference group also had a baseline and acupuncture scan, although the acupuncture itself was performed using a standardized set of needle points. RESULTS The reference group participants were found to have significant increases in the thalamic and prefrontal cortex activity on the acupuncture scan compared to the baseline. The baseline scans of the pain patients showed significant asymmetric uptake in the thalami compared to controls. This asymmetry reversed or normalized after the acupuncture therapy. Significant correlations were observed between the change of activity in the prefrontal cortex and ipsilateral sensorimotor area. CONCLUSION The results from these cases show that HMPAO-SPECT is capable of detecting changes in cerebral blood flow associated with pain and that acupuncture analgesia is associated with changes in the activity of the frontal lobes, brain stem, and thalami.