Effect of low intensity laser (830 nm) irradiation on skin temperature and antidromic conduction latencies in the human median nerve: Relevance of radiant exposure

Abstract

The effects of low intensity near-infrared laser radiation (830 nm; 1.5-12 J/cm2; continuous wave) on peripheral neurophysiology and skin temperature were investigated using antidromic conduction studies in the human median nerve in vivo. Healthy human volunteers (n = 80) were recruited and randomly allocated to one of two control (n = 30) or five laser groups (1.5, 3.0, 6.0, 9.0, and 12 J/cm2; n = 10 per group). Analysis of variance (ANOVA) in negative peak latency difference scores (NPLDs) and skin temperature over a 20 min period post-irradiation demonstrated a significant decrease in skin temperature following irradiation at the lowest radiant exposure (1.5 J/cm2) coupled with a significant increase in NPLDs (P < 0.05). While no such (significant) changes were found in the other laser groups, it was found that observed changes (increases and decreases) in NPLDs were inversely related to changes in skin temperature. These findings demonstrate measurable peripheral neurophysiological effects of laser radiation concomitant with changes in skin temperature; however, further studies are indicated to establish the precise relationship between the observed effects on skin temperature and nerve conduction.