The 980-nm diode laser as a new stimulant for laser evoked potentials studies

Background and Objective: Lasers have been used as stimulators for creating pain response without stimulating mechanoreceptive fibers. Various laser s ystems are still under investigation on the quest for best laser system. Ou r objective was to test the feasibility of the 980-nm diode laser for LEP ( laser evoked potentials) studies. Study Design/Materials and Methods: Laser evoked potentials created by usin g the 980-nm diode laser were recorded by using standard electroencephalogr am (EEG) techniques. The collimated laser beam was 3 mm in diameter. Stimul us duration was set to 200 msec. The power of laser stimulus exposed to the dorsum of the right hand of 10 healthy volunteer subjects (5 women and 5 m en) was varied between 0 and 10 watts to determine the pain threshold. EEG signals during the exposure of 1.5 times the threshold value were recorded from scalp electrodes placed on areas Fz, Ct, Pt, C3, and C4 according to t he international 10-20 system. The stimulus presented during the EEG record ing was described as a bearable pain sensation like a pinprick perception b y the subjects. After 0.1-30 Hz analog low-pass filtering, 100-msec prestim ulus, and 900-msec poststimulus EEG epochs were recorded at 256 Hz sampling rate and evaluated statistically. Thirty stimuli were presented by randoml y varying the interstimulus duration between 5 and 9 seconds. Results: Latency and amplitude values of LEPs were found in accordance with those reported in the literature. Conclusion: The 980-nm diode laser used is a suitable stimulator for LEP st udies. (C) 2001 Wiley-Liss, Inc.