Introduction: Chronic upper extremity pain (UEP) has several etiologies, can often be disabling with current treatments offering only limited symptom relief. Traditional low-frequency spinal cord stimulation (SCS), although successful in treating UEP, is limited by variability in sensory paresthesia with movement of upper extremities, thus potentially compromising pain relief. SCS at 10 kHz, on the other hand, has been demonstrated to provide superior pain relief without any paresthesia. Thus, the objective of this prospective, multi-center, post-market, observational study was to gain additional effectiveness data of SCS at 10 kHz for the treatment of chronic, intractable pain of the upper extremities.
Materials and Methods: A total of 38 subjects, with significant upper extremity pain (Visual analog scale [VAS] ≥ 5 cm at baseline) underwent a trial phase of SCS at 10 kHz at five centers in the United States and one center in the United Kingdom. The study protocol and informed consent were approved by the Institutional Review Board/Ethics Committee at each clinical site. Patient outcomes were assessed for a period of 12 months; and the primary outcome of the study was the responder rate (percentage of patients experiencing ≥ 50% pain relief from baseline). Other assessments included upper limb functioning (Disability of Arm, Shoulder and Hand; QuickDASH), pain disability index (PDI), sleep, global assessment of functioning (GAF) and subject satisfaction.
Results: Thirty-seven subjects successfully completed the trial (97.4% trial success) and consequently were permanently implanted with the Senza SCS system. Three months after permanent device activation, the responder rates for upper limb, shoulder and neck pain patients were 80.8%, 72.7% and 68.4%, respectively, with mean VAS scores reducing from 7.8 ± 1.1 cm (n=36) to 2.2 ± 2.5 cm (n=26), 8.1 ± 1.1 cm (n=31) to 2.7 ± 2.7 cm (n=22) and 8.2 ± 1.3 cm (n=28) to 2.8 ± 2.8 (n=19), respectively. Significant improvements in functioning, quality of life, disability and sleep were also observed. Global PDI scores decreased from 46.1 ± 12.5 to 22.0 ± 18.7. Over three-fourths (80.8%) of the subjects showed a clinically meaningful decrease in QuickDASH.
Conclusion: SCS at 10 kHz has previously demonstrated superior pain relief in the treatment of back and leg pain as compared to traditional low-frequency SCS. Preliminary results from this study suggest that this therapy can also provide sustained and significant pain relief in subjects with UEP. Clinically significant increases in functioning and quality of life were also observed in majority of patients. These results thus validate that SCS at 10 kHz is an effective and paresthesia-free treatment for chronic intractable pain of the upper extremities.