Activation of C-fiber nociceptors by low-power diode laser

Abstract

Objective: The evaluation of selective activation of C-fibers to record evoked potentials using the association of low-power diode laser (810 nm), tiny-area stimulation and skin-blackening. Method: Laser-evoked potentials (LEPs) were obtained from 20 healthy young subjects. An aluminum plate with one thin hole was attached to the laser probe to provide tiny-area stimulation of the hand dorsum and the stimulated area was covered with black ink. Results: The mean intensity used for eliciting the ultra-late laser-evoked potential (ULEP) was 70 +/- 32 mW. All subjects showed a clear biphasic potential that comprised a negative peak (806 +/- 61 ms) and a positive deflection (1033 +/- 60 ms), corresponding to the ULEP related to C-fiber activation. Conclusion: C-fiber-evoked responses can be obtained using a very low-power diode laser when stimulation is applied to tiny areas of darkened skin. This strategy offers a non-invasive and easy methodology that minimizes damage to the tissue.