32. Effect of focal mechanical vibration on the nociceptive pathways.

Our aim was to evaluate whether the focal application of a vibratory stimulation on the skin may change the laser evoked potentials (LEPs) and the laser- pain to pulses delivered on the same cutaneous area. In 10 healthy volunteers, LEPs were recorded after stimulation of the radial and ulnar dorsal hand territories, bilaterally. After each LEP recording, the subjects were asked to rate the laser-pain according to a 100-point VAS. All subjects were evaluated in two different sessions in order to test both effective and sham vibratory stimulation. In each session, the experiment included 2 times: (1) LEPs were recorded without any conditioning vibratory stimulus, (2) LEPs were recorded during effective or sham vibratory stimulation within the right radial territory. No difference in N2/P2 amplitude changes was found between the effective and the sham vibratory stimulation. Also the subjective perception of pain was not influenced by the simultaneous vibratory (effective or sham) stimulation. Our negative results suggest that focal vibratory stimuli, currently used for motor rehabilitation, are not effective as analgesic physical treatment. [Copyright &y& Elsevier]