Abstract|Pain 1| Volume 357, SUPPLEMENT 1, e90, October 15, 2015

Somatosensory evoked potentials to painful and painless electrical stimulation (SSEPEES). A tool for the clinical assessment of neuropathic pain pathways?

      Background: SSPEs with N1 latency of ~140 ms and Ad range velocity are recorded with painful and painless electrical stimulation (ring electrodes). Intradermal electrodes have been used for specific stimulation of the thermoalgesic pathways. Similar potentials are obtained with other sensory modalities, described as reflecting the saliency rather than the nature of the stimuli.
      Objective: To reassess whether recorded SSPEs can reliably index their afferent pathway function.
      Methods: 26 controls, mean age 41 years ± SD13.1 (range27-71). VAS graded stimulation (ring electrodes) to 3rd finger and 2nd toe with 2 stimuli of 0.5 ms and ISI = 5 ms at frequencies between 0.1-1Hz. Recordings at Cz-A1A2 (ten 2 s epochs averaged twice). The effect of compression block, and of magnetic and heat stimulation (CHEPS, Medoc) were also investigated. Subject consent and institutional approval obtained.
      Results: N1-P1 amplitude increased with increasing VAS graded stimulus intensity. N1 latency across VAS grades did not change. No potentials recorded with threshold stimuli (VAS = 0). Mean N1-P1 amplitude decreased with increasing stimulation frequency. No change in amplitude was seen for each of 4 levels of VAS graded stimuli when their order of presentation was changed. Magnetic and heat stimulation elicited similar potentials. Arm compression block resulted in diminishing N1 amplitude and paraesthesiae at 5 min, unrecordable at 15 min (cold perceived as hot and light touch and pinprick absent then), and unrecordable potential at 20 min.
      Conclusion: N1-P1 amplitude and latency at 0.1 Hz seem robust parameters. Further testing in patients with thermoalgesic pathways pathology is advisable.
      *Fondecyt 1120339: LAcevedo, GBarraza, MCampero, JLCastillo, GCavada, RJGuiloff, JHoneyman, JMMatamala, EMullins, POrellana, CRamirez, HRojas, ISazunic, RVerdugo, YWang.