Individually based measurement of temporal summation evoked by a noxious tonic heat paradigm

Erica Suzan,1,2 Joshua Aviram,3 Roi Treister,4 Elon Eisenberg,1,2 Dorit Pud3 1Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, 2Institute of Pain Medicine, Rambam Health Care Campus, 3Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Israel; 4Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA Background: A model for measuring temporal summation (TS) by tonic noxious stimulation was recently proposed. However, methodological variations between studies make it difficult to reach a consensus regarding the way TS should be applied and calculated. The present study aimed to present a calculation method of TS magnitude produced by a tonic heat model in a large cohort of healthy subjects. Methods: Noxious heat stimulation (46.5°C/2 minutes) was applied to the forearm of 154 subjects who continuously rated pain intensity using a computerized visual analog scale. TS was calculated by “mean group” and “individual” approaches. Results: A “typical” pattern of pain response, characterized by a peak pain followed by a decrease in intensity to a nadir and subsequently a progressive increase in pain scores, was exhibited by 86.4% of the subjects. Using the "mean group" and "individual" calculation approaches, the mean ± standard deviation magnitudes of TS were 31.4±27.5 and 41.0±26.0, respectively (P<0.001). Additionally, using the individualized approach, we identified a different ("atypical") response pattern among the rest of the subjects (13.6%). Conclusion: The results support the tonic heat model of TS for future utilization. The individualized TS calculation method seems advantageous since it better reflects individual magnitudes of TS. Keywords: heat pain, healthy volunteers, individual differences, pain perception, temporal summatio