T83. Characterization of pain evoked potentials and skin innervations in capsaicin-induced reversible focal neuropathy

Abstract

Introduction This study aimed to investigate the temporal alterations of contact heat evoked potential (CHEP) in capsaicin-induced nerve degeneration and regeneration and its relationship to skin innervation density and thermal thresholds, in particular, whether the relationship between these parameters remained the same during different time points after topical capsaicin treatment. Methods We enrolled 14 normal subjects (7 men, age = 24.3 ± 2.5 years) to investigate intraepidermal nerve fiber (IENF) density, contact heat evoked potential (CHEP), and thermal thresholds at four time points including baseline, and first day, 3 weeks and 10 weeks after 2-weeks capsaicin application. Results After 2-weeks capsaicin treatment, IENF density was reduced with decreased amplitude and prolonged latency of CHEP, and increased warm and heat pain thresholds. Repeated measures ANOVA comparing the time course of IENF density, CHEP, pain rating and thermal threshold showed a significant effect of time on IENF density (F = 8.31, p Conclusion There was differential restoration of IENF density, CHEP and thermal thresholds, and discordant relationship between nociceptive nerve terminals and brain responses during the skin reinnervation after capsaicin-induced focal neuropathy.