Effect of acupuncture on perception threshold: a randomised controlled trial.

OBJECTIVE To determine the current perception thresholds (CPTs) for arm and mental foramen areas to enable a quantitative evaluation of the effectiveness of acupuncture treatment. METHODS Ninety-eight volunteers enrolled as participants and were randomly assigned to one of three groups: an acupuncture group (34 subjects); a sham acupuncture group (32 subjects) and a waiting group (32 subjects). CPTs for the arm and mental foramen areas were determined before and after acupuncture at LI4 Hegu of the left hand. A Neurometer CPT was used to evaluate the perception threshold at the homolateral mental foramen and arm. For further exploration, thresholds of homolateral and contralateral mental foramina were determined before and after acupuncture in a subgroup of 13 participants in the acupuncture group. RESULTS Acupuncture at LI4 increased the perception thresholds of the left mental foramen in the acupuncture group significantly (p<0.01). The increases were significantly greater than in the control group for all frequencies, and significantly greater than sham acupuncture for 250 Hz and 5 Hz. In the subgroup, only the CPTs at 5 Hz increased significantly for the contralateral mental foramen. CONCLUSIONS Acupuncture at LI4 increases the perception threshold in the mandibular area, but not in the arm. This finding is probably related to the analgesic effect of acupuncture.