Thulium laser somatosensory evoked potentials. Normative values for upper and lower limbs.

Laser somatosensory evoked potentials (LSEP) evaluate the functional integr ity of thermoalgic pathways by the specific stimulation of A delta and C no ciceptive afferences. As compared to a CO, laser, the thulium Yttrium Alumi nium Garnet (YAG) laser may be conducted by an optic fiber, which allows ea sier access to the stimulated body sites. We present normative data on thul ium YAG LSEPs recorded after stimulation of upper and lower limbs (N = 15). LSEPs were obtained with a stimulation intensity that was twice the nocice ptive threshold at the upper limbs (UL) and one and a half at the lower lim bs (LL). To ensure a stable attentional level, subjects were asked to estim ate stimulus intensity after each stimulation. The nociceptive thresholds a t upper and lower limbs were respectively 319 +/- 65 mJ and 359 +/- 95, and with the above methodology the LSEPs could be obtained in every subject. T he latencies of N2 and P2 were respectively 199 +/- 18 ms and 325 +/- 37 ms at the UL, 239 +/- 36 ms and 378 +/- 38 ms at the CL. This method produced robust and reproducible results, and proved to be reliable for routine cli nical use. To optimise response stability we propose that right/left stimul ation be conducted following an 'A-B-B-A' procedure. (C) 2000 Editions scie ntifiques et medicales Elsevier SAS.