Papers of the Week

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. 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. 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 vs. 2 healthy subjects at temperatures of 39º and 41ºC. The study of adaptation to a constant temperature stimulus can furnish valuable data for the assessment of SPN patients.