• F Mahn, P Hüllemann, G Wasner, R Baron, and A Binder.
• Division of Neurological Pain Research and Therapy, Department of Neurology, Christian-Albrechts-Universität Kiel, Germany.
• Eur J Pain. 2014 Oct 1;18(9):1248-58.

BackgroundHuman experimental pain models play an important role in studying neuropathic pain mechanisms. The objective of the present study was to test the reproducibility of the topical menthol model over a 1-week period.MethodWe performed an open, two-period study in 10 healthy volunteers with 40 menthol applications. The side of menthol application was randomly assigned. Two trial periods were separated by 1 week. Before and after applying menthol, selected quantitative sensory testing (QST) was performed. The area of mechanical pin-prick hyperalgesia was quantified. Spontaneous pain was recorded.ResultsApplication of menthol induced a statistically significant decrease in the cold pain threshold (CPT) (p < 0.001) and mechanical pain threshold and an increase in the mechanical pain sensitivity (MPS) (p < 0.001), indicating cold and mechanical (pin-prick) hyperalgesia. Test-retest reliability was best for CPT (r = 0.959) and MPS (r = 0.930). Intraclass correlation values showed excellent reliability for cold pain and MPS (ICC = 0.96, 0.89). The QST values post-menthol showed high inter-period correlation factors and no significant inter-period differences (paired t-test, t = 1.767-1.361; p = 0.111-0.988). The area size of mechanical hyperalgesia was not reliably reproducible.ConclusionFor an observation period of 1 week, the signs of cold and mechanical hyperalgesia were reproducible with a highly significant correlation of about r = 0.8 and good agreement except for the area size of mechanical pin-prick hyperalgesia. These results demonstrate that the topical menthol pain model is suitable for pharmacological interventions repeated within an observation period of 1 week.© 2014 European Pain Federation - EFIC®

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