gms | German Medical Science

Introduction: Pain sensation is of high importance in Rheumatoid Arthritis (RA) patients as inflammation triggers pain development strongly. Although the etiology of pain in RA has a primarily nociceptive character, up to 20% of RA patients suffer from a neuropathic pain component and sensitization. Thus, pain cannot only be interpreted as a reflection of disease activity but may also indicate neuropathic changes and chronicity.

Methods: To examine the effects of chronic inflammation on pain sensation and neuropathy development 16 RA patients (mean age: 59.38y [±10.18]) with controlled disease (DAS28 low disease activity or remission) were compared to healthy subjects (HS; mean age: 56.69y [±8.92]). We used the quantitative sensory testing (QST; standardized test battery of 7 thermal and mechanical stimuli, measuring 13 parameters) protocol of the German Research Network on Neuropathic Pain (DFNS) and Electroencephalography-(EEG)-based contact heat evoked potentials (CHEPs; heat stimuli of 54°C, causing measurable potentials in EEG). QST and CHEPs were applied on the hand and on the thigh before and after topical capsaicin application in RA patients and HS.

Results: QST showed a lower pressure pain threshold (PPT) of the hand in RA than HS (p = 0.026). Moreover, the application of capsaicin cream (0.2% capsaicin in DAC base cream) on the thigh provoked a stronger separation effect in HS for heat pain thresholds (HPT) according to the Area Under the Receiver Operation Curve (AUROC) (HS: 0.8965, p<0.0001; RA: 0.7012, p=0.0316). We observed different effects of capsaicin cream regarding changes in CHEPs (HS: g*max = -0.65; RA patients: g*max = 0.72).

Conclusion: According to the AUROC values, topical capsaicin application evoked a greater sensitization effect in HS for heat pain stimuli. Chronic inflammation in RA might lead to a sensitization of heat- and capsaicin sensitive TRPV1 channels of nociceptors. CHEPs amplitudes may uncover neuropathic symptoms in RA patients, shown by a decreased amplitude before capsaicin application. The effect of topical capsaicin on HPT and CHEPs may act as a marker for the extent of sensitization and development of neuropathic pain symptoms with the potential to predict and track treatment response on pain symptoms.

Figure 1 [Fig. 1]

Disclosures: Björn Anders: None declared, Malte Anders: None declared, Michaela Köhm Grant/research support from: Pfizer, Janssen, BMS, LEO, Consultant of: BMS, Pfizer, Speakers bureau: Pfizer, BMS, Janssen, Novartis, Gerd Geisslinger: None declared, Frank Behrens Grant/research support from: Pfizer, Janssen, Chugai, Celgene, Lilly and Roche, Consultant of: Pfizer, AbbVie, Sanofi, Lilly, Novartis, Genzyme, Boehringer, Janssen, MSD, Celgene, Roche and Chugai, Carmen Walter: None declared