Spinothalamic tract conduction velocity estimated using contact heat evoked potentials: what needs to be considered.
OBJECTIVE
Laser-evoked potentials have been shown to be clinically useful for the electrophysiological assessment of nociceptive pathways. Contact heat evoked potentials (CHEP) are less established but might be advantageous for clinical purposes. This study aimed at determining the conduction velocity (CV) of central pain (spinothalamic tract, STT) pathways using contact heat stimulation in order to replicate previous findings using laser stimulation.


METHODS
Contact heat stimulation 3 degrees C higher than the pain threshold was applied at different body locations in 20 subjects.


RESULTS
The CHEP latencies correlated significantly with the respective pain thresholds. Without normalization for this effect no significant linear regression between distance to the brain and the latencies was found. Conversely, if thresholds were considered, the regression was significant and the CV of the STT (ranging between 11.2 and 13.4m/s) was comparable to CVs estimated after laser stimulation.


CONCLUSIONS
Pain thresholds seem crucial in interpreting CHEP latencies. It is suggested that the rather low heating rate is responsible for the dependence of latencies on the pain thresholds.


CONCLUSIONS
This study shows the importance of pain thresholds and their control to attain valid CV of the STT after contact heat stimulation in healthy subjects.
Wydenkeller
Susanne
S
Spinal Cord Injury Centre, University Hospital Balgrist, Forchstrasse 340, 8008 Zurich, Switzerland.
Wirz
Regula
R
Halder
Pascal
P
D000328:Adult; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009431:Neural Conduction / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology*; D013133:Spinothalamic Tracts / Q000502:physiology*; D013697:Thermosensing / Q000502:physiology