P993: Circadian hyperactivity of the lower limb nociceptive system in idiopathic restless legs syndrome: a CO2 laser evoked potential study

Abstract

Aim of the study was to assess the A-delta nociceptive system during the night and afternoon in idiopathic Restless Legs Syndrome (RLS) patients, by recording the Laser Evoked Potentials (LEPs). We studied 11 patients (mean age 53.40 ± 18.59 years; 6 males, 5 females) affected by idiopathic RLS. LEPs were recorded to stimulation of the right foot, hand and perioral region. LEPs were recorded at night (between 9.00 PM and 11.00 PM) and in the early afternoon (between 1.00 PM and 3.00 PM). Two consecutive averages (20 trials each) were obtained for each stimulation site. LEPs were recorded from 3 recording electrodes placed at Cz, Fz, and T3 sites of the 10–20 International System. In RLS patients, we found a significant increase of N2–P2 amplitude after foot stimulation during nighttime session ( p = 0.008) when compared to daytime. The N2/P2 amplitude after hand and face stimulation was not significantly different during both sessions ( p > 0.05). We did not find any impairment of the Adelta-fiber system. However, there is a prevailing activity of the Adelta nociceptive system of lower limbs during nighttime. These findings suggest, in idiopathic RLS, a circadian disinhibition in the central processing of the lower limb Adelta-fiber inputs.