Higher score measuring severity of pain indicated elevated treatment failure risk.
Many patients with both type 1 and type 2 diabetes suffer from painful diabetic peripheral neuropathy (PDPN). Patients with this complication experience irreversible peripheral nerve damage resulting in severe pain, which is difficult to manage. The pain can become so unbearable and potentially interfere with quality of life. There are no medications that can prevent the progression or even reverse the disorder. Medications available are only to help relieve pain and are a lot of times inadequate for pain relief. Spinal cord stimulation (SCS) was introduced as last-resort therapy and has been around for years now. Previous studies have suggested that SCS is efficacious in short follow-up studies. However, no long-term studies have been conducted as of yet.
The goal of the following prospective multicenter study was to evaluate the effects of SCS on patients with PDPN over a period of five years. The study measured SCS success, failure, and associated complications. A total of 48 participants with PDPN were included in the study from the outpatient pain clinics of the Maastricht University Medical Center and the Radbound University Medical Center (UMC). The level of neuropathy severity was determined through use of The Michigan Diabetic Neuropathy Score (MDNS). Patients were included if they experienced pain relief during the initial SCS implantation trial. Patients were also included if they had inadequate pain relief and/or experienced side effects with their current drug treatment. They also had to have history of complications for a period longer than 12 months and a mean numeric rating scale (NRS) pain score of 5 or greater.
At baseline, parameters obtained included diabetes duration, pain duration, NRS pain score, MDNS, type of diabetes, height, weight, age, sex, and HbA1c. Follow-up was conducted 12 months after baseline measurement followed by once yearly for the remainder of the study. Treatment was considered successful if patients experienced at least a 50% reduction in the NRS day and night pain score or if they had a Patient Global Impression of Change (PGIC) pain and sleep score of at least 6 out of 7 on a Likert scale. Treatment was considered a failure if use of the SCS system was discontinued and removed. Patients were considered to have complications if they had to visit for technical difficulties or adverse effects.
According to results, it was found that 42% of patients had an NRS pain score reduction of at least 50% throughout the day after 1 year, 43% after 2 years, 47% after 3 years, 37% after 4 years, and 36% after the 5 year follow-up. In regards to pain throughout the night, 36% of patients experienced pain reduction of at least 50% after 1 year, 40% after 2 years, 35% after 3 years, 33% after 4 years, and 32% after the 5-year follow-up. According the PGIC pain and sleep scale results, percentage of patients that chose the option of “very much improved,” were 72% and 53% after 1 year, 54% and 37% after 2 years, 53% and 29% after 3 years, 53% and 47% after 4 years, and 50% and 32% after the 5-year follow-up.
Overall, 86% of patients experienced successful therapy following 1 year, 71% after 2 years, 77% after 3 years, 67% after 4 years, and 55% after the 5-year follow-up. After the 5-year period, 80% of patients were still using their SCS systems. Through use of univariate Cox proportional hazards regression, it was determined that a higher MDNS was related to a significantly higher treatment failure risk. (Hazard ratio (HR) 3.9, 95% CI 1.3 to 11.6, P=0.014).
The study showed that in patients with PDPN, SCS therapy for an extended period of 5 years is successful at reducing severe pain in the lower limbs. At the end of the study there was still a significant number of patients using SCS therapy. It was also determined that in patients with a higher MDNS, the chance of failing long-term treatment is elevated. Although the study had positive results, a limitation to consider is that the study did not include a control group.
- Long-term SCS therapy was successful at improving chronic pain in patients with PDPN that had failed other pain therapies.
- SCS therapy was still being used by 80% of patients at the end of the 5-year period.
- Higher MDNS resulted in elevated treatment failure risk.
Van Beek M, Geurts JW, Slangen R, et al. Severity of Neuropathy Is Associated With Long-Term Spinal Cord Stimulation Outcome in Painful Diabetic Peripheral Neuropathy: Five-Year Follow-up of a Prospective Two-Center Clinical Trial. Diabetes Care. 2017; 0:1-7.
Graciela Nieto, Pharm. D. Candidate 2018, LECOM School of Pharmacy