EFFECTS OF LOW-INTENSITY INFRARED-LASER IRRADIATION UPON CONDUCTION IN THE HUMAN MEDIAN NERVE IN-VIVO

The current investigation, for which ethical permission was obtained, was designed to assess the putative neurophysiological effects of low intensity (9.6 J/cm2) laser (830 nm) irradiation upon conduction laten cies in the human median nerve in vivo. Antidromic nerve conduction st udies were performed on the non-dominant arms of healthy human volunte ers (n = 51), who were each assigned to one of a variety of laser, pla cebo or control groups under randomized, blinded conditions. Analysis of negative peak latency differences using analysis of variance showed small (approximately 0.4 ms) but significant increases in latencies a s a result of direct laser irradiation, and, where two-site recording was used, distal to the site of irradiation. No such differences were seen in the other experimental groups. These results show that laser i rradiation applied to intact skin at the parameters used here may prod uce a direct, localized effect upon conduction in underlying nerves.