Objective correlate of subjective pain perception by contact heat-evoked potentials.
The method of pain-evoked potentials has gained considerable acceptance over the last 3 decades regarding its objectivity, repeatability, and quantifiability. The present study explored whether the relationship between pain-evoked potentials and pain psychophysics obtained by contact heat stimuli is similar to those observed for the conventionally used laser stimulation. Evoked potentials (EPs) were recorded in response to contact heat stimuli at different body sites in 24 healthy volunteers. Stimuli at various temperatures were applied to the forearm (43 degrees C, 46 degrees C, 49 degrees C, and 52 degrees C) and leg (46 degrees C and 49 degrees C). The amplitudes of both components (N2 and P2) were strongly associated with the intensity of the applied stimuli and with subjective pain perception. Yet, regression analysis revealed pain perception and not stimulus intensity as the major contributing factor. A significant correlation was found between the forearm and the leg for both psychophysics and EPs amplitude.


CONCLUSIONS
Contact heat can generate readily distinguishable evoked potentials on the scalp, consistent between upper and lower limbs. Although these potentials bear positive correlation with both stimulus intensity and pain magnitude, the latter is the main contributor to the evoked brain response.
Granovsky
Yelena
Y
Department of Neurology, Rambam Medical Center, and the Laboratory of Clinical Neurophysiology, Technion Faculty of Medicine, Haifa, Israel. davidy@tx.technion.ac.il
Granot
Michal
M
Nir
Rony-Reuven
RR
Yarnitsky
David
D
D000328:Adult; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005121:Extremities / Q000294:innervation / Q000502:physiology; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold / Q000502:physiology*; D010465:Perception / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology; D010812:Physical Stimulation / Q000009:adverse effects; D011237:Predictive Value of Tests; D011601:Psychophysics / Q000379:methods; D012044:Regression Analysis; D012535:Scalp / Q000294:innervation / Q000502:physiology; D012680:Sensitivity and Specificity; D011984:Sensory Receptor Cells / Q000502:physiology; D012867:Skin / Q000294:innervation; D013697:Thermosensing / Q000502:physiology*