Exploring Psychophysical and Neurophysiological Responses to Intra-Epidermal Electrical Stimuli in Patients With Persistent Spinal Pain Syndrome Type 2 with a Spinal Cord Stimulator

There is a lack of measures that provide insights into how spinal cord stimulation (SCS) modulates nociceptive function in patients with persistent spinal pain syndrome type 2 (PSPS-T2). Recently, we observed altered nociceptive detection thresholds (NDTs) in response to intra-epidermal electrical stimulation (IES) on the feet of PSPS-T2 patients when dorsal root ganglion stimulation was turned on. Furthermore, we observed altered NDTs and evoked potentials (EPs) in response to IES on the hands of PSPS-T2 patients. To explore whether EPs were obstructed by SCS artifacts, we applied IES twice to the hands of patients with SCS turned on (SCS-ON/ON group). To explore possible confounding effects of SCS outside the stimulated area, we repeated IES on the hands of these patients, once with SCS turned off and subsequently once with SCS turned on (SCS-OFF/ON group). The results demonstrated that EPs were not obstructed by SCS artifacts. Additionally, NDTs and EPs did not significantly change between measurements in the SCS-ON/ON and the SCS-OFF/ON groups. Therefore, the results suggested that possible confounding effects of SCS outside the nociceptive system did not interfere with the detection task performance. This work warrants further exploration of NDT-EP phenomena in response to IES at the painful feet of patients.