The Effect of Light Therapy on Superficial Radial Nerve Conduction Using a Clustered Array of Infrared Super luminous Diodes and Red Light Emitting Diodes

Introduction: Lasers, light emitting diodes (LEDs) and super luminous diodes (SLDs) are widely used to treat selected musculoskeletal, integumentary and neurological conditions. The mechanisms underlying the reported treatment effects of light therapy are unclear and the physiologic effect of light on a variety of tissues, particularly neurological, is mostly unknown. A few researchers have reported on the effects of lasers and to a lesser extent infrared LEDs on nerve conduction in superficial nerves, but there is little evidence of the effects of SLDs and red LEDs on conduction parameters of peripheral nerves. The purpose of this study was to examine the effects of a light therapy generated by cluster probe containing an array of infrared super luminous and red light emitting diodes on superficial radial nerve conduction. Methods: This was a single blind, randomized controlled trial conducted in an academic clinical laboratory. Thirty-two healthy participants (mean age = 25 years) were randomized to a treatment group or a placebo group. The treatment group received light irradiation through the application of a cluster probe containing 32 infrared (880nm) SLDs and 4 red (660nm) LEDs for 30 seconds at a dose of 6 J/cm2 to each of the two 5 cm2 segments of skin overlying the superficial radial nerve. The placebo group received identical set-up without the application of light irradiation. Negative peak latency (NPL) and conduction velocity (NCV) for the superficial radial nerve were measured before treatment and for 10-minutes following treatment at 2-minute intervals. Skin temperature was monitored throughout. Results: No significant differences between groups and over time for NPL, NCV, or temperature difference scores were identified. However, a significant increase in skin temperature was measured over time at each time point compared to baseline Conclusion: Light irradiation using a cluster probe containing infrared super luminous and red light emitting diodes does not impact the neurophysiological properties of the superficial radial nerve.