Clinical utilization of fast-acting sub-perception therapy (FAST) in SCS-implanted patients for treatment of mixed pain.

A significant proportion of patients with chronic pain exhibit mixed pain and thus do not display symptoms exclusively associated with either nociceptive or neuropathic pain syndromes. We aimed to explore whether Fast-Acting Sub-Perception Therapy, FAST - a new Spinal Cord Stimulation (SCS)-based approach capable of inducing a rapid-onset of analgesia using electrical neurostimulation applied below patient-perception threshold - could potentially be useful as a treatment for chronic mixed pain. Fourteen consecutively-enrolled patients diagnosed with chronic mixed pain and implanted with an SCS device were enrolled in this single-center case-series. All patients completed a validated, self-administered painDETECT questionnaire prior to SCS-device implantation (baseline). The painDETECT questionnaire was used to characterize each patient's chronic pain as likely neuropathic only, uncertain (but potential for presence of a non-neuropathic component), or likely presence of a non-neuropathic component. Overall pain scores (Numeric Rating Scale, NRS), Oswestry Disability Index (ODI) and Quality-of-life (EQ-5D-5L) were collected (per standard-of-care) at baseline, 3-months, and 6-months post-implantation. The average age of those assessed in this study was 64.7 ​± ​11.5 (SD) years and 43% (6/14) were female. Fifty-percent (7/14) of patients were classified with non-neuropathic pain (painDETECT), while the remainder exhibited chronic pain that could not be characterized as either neuropathic or non-neuropathic (uncertain). Mean overall pain (NRS) among all patients was 8.3 ​± ​0.3 (SE) at baseline. At 6-months post-implant, a mean 6.9-points NRS score reduction was observed (1.4 ​± ​0.3 (SE); p ​< ​0.0001). Notable improvements in disability (ODI) and Quality of Life (EQ-5D-5L) were also observed at 6-month follow-up. The data from this observational case-series indicate that FAST-SCS can improve outcomes in patients reporting complex symptoms of mixed pain with a likely non-neuropathic component. These results suggest that neurostimulation modalities such as FAST may be a suitable treatment approach for non-neuropathic pain indications.