Painful Cutaneous Electrical Stimulation vs. Heat Pain as Test Stimuli in Conditioned Pain Modulation

Abstract

Different paradigms can assess the effect of conditioned pain modulation (CPM). The aim of the present study was to compare heat pain, as an often used test stimulus (TS), to painful cutaneous electrical stimulation (PCES), having the advantage of the additional recording of PCES-related evoked potentials. In 28 healthy subjects we applied heat and PCES at the dominant hand as test stimulus (TS) to compare the CPM-effect elicited by hand immersion into cold water (10 °C) as conditioning stimulus (CS). Subjects rated the pain intensity of TS at baseline, during and 5 min after CS application and additionally of CS, on a numerical rating scale (NRS) (0–100). The ‘early’ (during CS–before CS) and ‘late’ (after CS–before CS) CPM-effects were analyzed. Parallel to the PCES, the related evoked potentials were recorded via Cz to evaluate any changes in PCES-amplitudes. CS reduced significantly the pain intensity of both PCES and heat pain as TS. On a group level, the CPM-effect did not differ significantly between both paradigms. Both early and late CPM-effect based on PCES correlated significantly with the CS pain intensity (r = −0.630 and −0.503, respectively), whereas using heat pain the correlation was not significant. We found a significant reduction of PCES-amplitudes during CS, but this did not correlate with the PCES-induced pain intensity. Correlation with the CS painfulness (r = −0.464) did not achieve the significance level after Bonferroni correction. The extent of the CPM effects was similar in both testing paradigms at group level, despite intraindividual differences. Future studies should further elicit the exact mechanisms explaining the modality of these specific differences.

Posttraumatic headache: pain related evoked potentials (PREP) and conditioned pain modulation (CPM) to assess the pain modulatory function

“…The aim of the study was to investigate the pain modulatory function in patients with PTH as a possible contributing mechanism, based on a novel recently established testing paradigm CPM 35 , 41 , 42 including electrophysiological parameters after electrical stimulation as an objective readout. Additionally, we recorded PREP as previous studies on primary headaches and trigeminal neuralgia indicated that increased PREP amplitudes might be useful as a marker for central sensitisation 16 , 43 , 44 .…”

Comparison of Thermal and Electrical Modalities in the Assessment of Temporal Summation of Pain and Conditioned Pain Modulation

“…Indeed, as mentioned previously, different modalities (thermal, mechanical, electrical, etc.) used as TS and/or CS appear to vary in their ability to evoke CPM or TSP ( 30 , 36 – 38 ). While these studies differ somewhat in the specifics of their findings, a general emerging trend suggests that electrical stimulation (either as the TS, the CS, or both) tends to be less suited than other types of stimulation to evoke CPM.…”

No relevant differences in conditioned pain modulation effects between parallel and sequential test design. A cross-sectional observational study

“…Little is known however about potential differences in the magnitude of the CPM effect between a sequential or parallel design. Indirect studies reported conflicting results, showing no differences between both designs ( Ibancos-Losada et al, 2020 ), larger effects for either a parallel ( Nahman-Averbuch et al, 2013 ; Ram et al, 2008 ) or sequential ( Enax-Krumova et al, 2020 ) design. Moreover, statistical comparisons between the two designs were often not performed ( Enax-Krumova et al, 2020 ; Nahman-Averbuch et al, 2013 ; Ram et al, 2008 ).…”