Effect of Sensory Sensitivity on Pain Processing Following Noxious Electrical Stimulation in Healthy Participants

Abstract

The purpose of this study was to investigate the influence of sensitivity to sensory input, including pain, on the conditioned pain modulation (CPM) effect of oxious Electrical Stimulation (NxES). Seventeen healthy participants (24.8 (+/- 2) years) were enrolled in this study that was approved by the IRB. Each person participated in a familiarization session, and 2 testing sessions 24 hours apart. Sensory sensitivity was assessed with the Sensory Hypersensitivity Scale, touch and heat/cold detection thresholds. Pain sensitivity was assessed with the Pain Sensitivity Questionnaire, heat/cold pain thresholds, and pressure pain threshold (PPT). Pain modulation was assessed with temporal summation (TS) and CPM involved a test stimulus of PPT and conditioning stimulus was immersion in a cold water bath for 2 min. The NxES: 20 min of electrical stimulation (400 μs pulse duration, 50 pulses/s; 10s on:10s off; intensity was maximum tolerated). The difference between PPT before and after the NxES comprised the treatment effect. Neither Sensitivity to touch or temperature sensations nor pain sensitivity related to the treatment effect of the NxES. A higher the amplitude of pain perception of NxES was associated with greater treatment effect. The NxES was effective in inhibiting pain and reduced the extent of pain facilitation 24 hours after the treatment. CPM was no different after the NxES. The finding suggests that people who are more sensitive to sensations also experience pain inhibition from NxES. The nervous system is not as “reactive” to pain after a treatment of NxES and the lack of change in the CPM after the treatment of NXES suggests that artificially inducing pain inhibition with NXES does not interfere with the normal pain inhibitory function of the nervous system. Thus, any inhibition due to NXES treatment could augment that which is produced by a patient's own nervous system. The purpose of this study was to investigate the influence of sensitivity to sensory input, including pain, on the conditioned pain modulation (CPM) effect of oxious Electrical Stimulation (NxES). Seventeen healthy participants (24.8 (+/- 2) years) were enrolled in this study that was approved by the IRB. Each person participated in a familiarization session, and 2 testing sessions 24 hours apart. Sensory sensitivity was assessed with the Sensory Hypersensitivity Scale, touch and heat/cold detection thresholds. Pain sensitivity was assessed with the Pain Sensitivity Questionnaire, heat/cold pain thresholds, and pressure pain threshold (PPT). Pain modulation was assessed with temporal summation (TS) and CPM involved a test stimulus of PPT and conditioning stimulus was immersion in a cold water bath for 2 min. The NxES: 20 min of electrical stimulation (400 μs pulse duration, 50 pulses/s; 10s on:10s off; intensity was maximum tolerated). The difference between PPT before and after the NxES comprised the treatment effect. Neither Sensitivity to touch or temperature sensations nor pain sensitivity related to the treatment effect of the NxES. A higher the amplitude of pain perception of NxES was associated with greater treatment effect. The NxES was effective in inhibiting pain and reduced the extent of pain facilitation 24 hours after the treatment. CPM was no different after the NxES. The finding suggests that people who are more sensitive to sensations also experience pain inhibition from NxES. The nervous system is not as “reactive” to pain after a treatment of NxES and the lack of change in the CPM after the treatment of NXES suggests that artificially inducing pain inhibition with NXES does not interfere with the normal pain inhibitory function of the nervous system. Thus, any inhibition due to NXES treatment could augment that which is produced by a patient's own nervous system.