Adaptation to tonic heat in healthy subjects and patients with sensory polyneuropathy

Abstract

Background: Adaptation to a constant sensory stimulus involves many sites along the path of sensory volleys towards perception. The evaluation of such phenomenon may be of clinical interest. We studied adaptation to a constant temperature stimulus in healthy subjects to set normative data and in patients with sensory polyneuropathy (SPN), as proof of concept.Methods: Twenty-six healthy subjects and 26 patients with SPN in the context of chemotherapy treatment with oxaliplatin for colon cancer were instructed to express through an electronic VAS system (eVAS); the level of sensation felt when a thermode set at either 39º, 41º, 43º, 45º or 47º was applied to their ventral forearm. Results:The eVAS recordings showed typically an abrupt onset that slowed to approach maximum sensation and continued with a slow decrease indicating adaptation. The time to respond (TR), the velocity of the initial response (VR), the maximum sensation (MA), the time to reach MA (MAt), the onset of adaptation (AO) and the decrease in the sensation level with respect to MA at 30 s after stimulus application (SL30), were dependent on the temperature level in all subjects. However, patients showed significantly delayed TR, slowed VR, decreased MA, delayed AO and reduced SL30, with respect to healthy subjects. Differences were more pronounced at low-temperature levels, with absent AO in 25 patients versus 2 healthy subjects at temperatures of 39º and 41ºC. Conclusion:The study of adaptation to a constant temperature stimulus can furnish valuable data for the assessment of patients with SPN. Significance:We studied perceptual changes in the intensity of thermoalgesic sensation during 30 s of constant temperature stimulation after an abrupt initial contact in healthy subjects and patients with sensory polyneuropathy. Patients showed delayed time to respond, decreased maximal sensation and reduced adaptation with respect to healthy subjects. Differences were more pronounced at low and intermediate temperatures (39ºC to 43ºC). The method is of easy implementation and shows clinically relevant abnormalities in patients with sensory polyneuropathy.

The Thermal Influence of an Electromagnetic Field with a Radio Frequency Depending on the Type of Electrode Used

“…In addition, the entire procedure was carried out in accordance with the guidelines of thermographic studies [ 29 , 30 ]. Another advantage of our work is the fact that the obtained results can be applied in clinical practice thanks to their compliance with relevant guidelines [ 28 , 29 ], which is in accordance with other researchers who used healthy volunteers as participants in similar studies [ 25 , 45 , 49 , 51 ].…”

“…For them, it would be more desirable to undergo the Indiba ® treatment using a capacitive electrode. On the other hand, in patients with disturbances in temperature sensation, such as in the course of, for example, polyneuropathy [ 45 ] and cavernosa of the spinal cord, it would be necessary to perform the procedure with a resistive electrode in order to stop the patient from experiencing pain.…”