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Summary Objective Laser-evoked potential (LEP) habituation was investigated under the influence of capsaicin-induced peripheral and central sensitization. Material and methods Fifteen subjects received 100 repetitive painful laser stimuli at the right hand dorsum at primary (application area; condition I) and secondary areas (beyond application area; condition II) in two different sessions after applying capsaicin topically. Conditions I and II were compared to a control condition without capsaicin application. N1, N2, and P2 latencies and N1 and N2/P2 amplitudes were recorded by EEG. Quantitative sensory testing (QST) and the Liewald Diary reaction time experiment were used as control tests. Results QST documented heat hyperalgesia as a sign of peripheral sensitization in the primary area and pinprick hyperalgesia in the primary and secondary area as a sign of central sensitization, after applying capsaicin. The N2/P2 amplitude habituation was significantly reduced in the primary area compared to controls (the primary area represents peripheral sensitization). The LEPs of the secondary area (the secondary area represents central sensitization) showed no significant N2/P2 amplitude habituation compared to controls. The comparison between conditions I vs. II showed no significant difference regarding N2/P2 amplitude and laser pain rating. Conclusion Capsaicin-induced central sensitization does not alter LEP habituation. The physiological habituation of LEP amplitudes is reduced due to peripheral mechanisms after applying capsaicin topically. These findings form a basis for future studies, which use the habituation paradigm to investigate pain conditions promoted by sensitization phenomena.

Objectives To evaluate the prevalence of ultrasonographic gout specific signs of foot joints. Methods This is a cross-sectional study which includes 15 patients with chronic gout, defined according to the American College of Rheumatology criteria (ACR 1977). Ultrasound (US) examination was performed using a high-frequency linear probe (Toshiba Xario®, frequency (8–14 MHz)) in B mode. 330 articular sites were studied at their dorsal surface. The ultrasound has objectified the presence of two signs: hyperechoic band over the superficial margin of the articular cartilage described as a double contour (DC) and tophaceous deposits at the joint cavity. Results The mean age at onset was 54.7±12,6 years, and the median diagnosis duration was 0 (0.3) years). The results of the US examination are summarized in Table 1. Conclusions This study showed a predilection for the gout specific ultrasound signs (DC and tophaceous deposits) in the tarsometatarsal and metatarsophalangeal joints, especially in the first MTP. The contribution of musculoskeletal ultrasound seems to be very interesting to objectify the presence of gout specific signs of the foot joints. Disclosure of Interest None declared

Objectives To compare the prevalence of ultrasonographic gout specific signs at the dorsal and plantar surfaces of the metatarsophalangeal joints (MTP). Methods This is a cross-sectional study which includes 15 patients with chronic gout, defined according to the American College of Rheumatology criteria (ACR 1977). Ultrasound (US) examination was performed using a high-frequency linear probe (Toshiba Xario®, frequency (8–14 MHz)) in B mode. 150 articular sites were studied at their dorsal and plantar surfaces. The ultrasound has objectified the presence of two signs: hyperechoic band over the superficial margin of the articular cartilage described as a double contour (DC) and the tophaceous deposits at the joint cavity. We compared the prevalence of the two signs between the dorsal and palmar surfaces at each site studied. Results The mean age at onset was 54.7±12,6 years, and the median diagnosis duration was 0 (0.3) years). The results of the US examination are summarized in Table 1. Conclusions Our study suggests that globally, DC predilect significatily in dorsal than in plantar surfaces of MTP joints. These results should be verified on a larger population. Disclosure of Interest None declared

Objectives To compare the prevalence of ultrasonographic gout specific sign double contour between the dorsal and palmar surfaces of the hand joints. Methods This is a cross-sectional study which includes 15 patients with chronic gout, defined according to the American College of Rheumatology criteria (ACR 1977). Ultrasound (US) examination was performed using a high-frequency linear probe (Toshiba Xario®, frequency (8–14 MHz)) in B and Doppler modes. 560 articular sites were studied at their dorsal and palmar surfaces. We compared the prevalence of the hyperechoic band over the superficial margin of the articular cartilage described as a double contour (DC) between the dorsal and palmar surfaces at each site studied. Results The mean age at onset was 54.7±12,6 years, and the median diagnosis duration was 0 (0.3) years). The results of the US examination are summarized in Table 1 Conclusions Our study suggests that globally, DC predilect significatily in dorsal than in palmar surfaces of hand joints. These results should be verified on a larger population. Disclosure of Interest None declared

Objectives To evaluate the prevalence of ultrasonographic gout specific signs of hand and fingers joints. Methods This is a cross-sectional study which includes 15 patients with chronic gout, defined according to the American College of Rheumatology criteria (ACR 1977). Ultrasound (US) examination was performed using a high-frequency linear probe (Toshiba Xario®, frequency (8–14 MHz)) in B mode. 540 articular sites were studied at their dorsal surface. The ultrasound has objectified the presence of two signs: hyperechoic band over the superficial margin of the articular cartilage described as a double contour (DC) and the tophaceous deposits at the joint cavity. Results The mean age at onset was 54.7±12,6 years, and the median diagnosis duration was 0 (0.3) years). The results of the US examination are summarized in Table 1. Conclusions This study showed a predilection for the gout specific ultrasound signs (DC and tophaceous deposits) of the wrist and MCP joints. The contribution of musculoskeletal ultrasound seems to be very interesting to objectify the presence of gout specific signs in the hand and fingers joints. Disclosure of Interest None declared

Background In the scientific approach to central processing of pain, the habituation phenomenon has been frequently described. Recent studies mentioned electrophysiological habituation during the recording of laser-evoked potentials (LEP). In this study we intended to test whether habituation can be reproducibly induced by repetitive painful laser stimuli and simultaneously measured with LEP. Inspired by findings from previous imaging studies that showed bilateral activation of the operculo-insular cortices, we hypothesized that repetitive painful laser stimuli applied to one hand lead to bihemispheral LEP amplitude habituation. Methods One hundred painful stimuli were applied to the right hand of 13 healthy subjects to induce contralateral N2P2 amplitude habituation. The left hand was stimulated 25 times before and after the right-hand stimulation to measure ispilateral LEPs; the experiment was sham controlled. Results We achieved significant contralateral N2P2 amplitude and pain habituation in all subjects. After central habituation was established, there was also a significant ispilateral N2P2 amplitude decrement (derived from the left hand) compared with baseline; in the sham condition, the N2P2 amplitude was unchanged. The pain sensation showed no habituation in both the painful stimulation condition and the sham condition. Conclusions Habituation (in the electrophysiological sense) is a physiological phenomenon that indicates normal central processing of pain in healthy controls. We showed bihemispheral N2P2 amplitude habituation after repetitive painful stimulation of the right hand. Our findings propose a bihemishperal contribution to central pain processing and pain modulation when electrophysiological habituation occurs.

In the scientific approach to central processing of pain, the habituation phenomenon has been frequently described. Recent studies mentioned electrophysiological habituation during the recording of laser-evoked potentials (LEP). In this study we intended to test whether habituation can be reproducibly induced by repetitive painful laser stimuli and simultaneously measured with LEP. Inspired by findings from previous imaging studies that showed bilateral activation of the operculo-insular cortices, we hypothesized that repetitive painful laser stimuli applied to one hand lead to bihemispheral LEP amplitude habituation.One hundred painful stimuli were applied to the right hand of 13 healthy subjects to induce contralateral N2P2 amplitude habituation. The left hand was stimulated 25 times before and after the right-hand stimulation to measure ispilateral LEPs; the experiment was sham controlled.We achieved significant contralateral N2P2 amplitude and pain habituation in all subjects. After central habituation was established, there was also a significant ispilateral N2P2 amplitude decrement (derived from the left hand) compared with baseline; in the sham condition, the N2P2 amplitude was unchanged. The pain sensation showed no habituation in both the painful stimulation condition and the sham condition.Habituation (in the electrophysiological sense) is a physiological phenomenon that indicates normal central processing of pain in healthy controls. We showed bihemispheral N2P2 amplitude habituation after repetitive painful stimulation of the right hand. Our findings propose a bihemishperal contribution to central pain processing and pain modulation when electrophysiological habituation occurs.