(24) Durable Improvement of Foot Sensation in Painful Diabetic Neuropathy via 10 kHz Spinal Cord Stimulation

Introduction: Approximately 20% of persons with diabetes will develop neuropathic or neurological symptoms, including loss of protective sensation. In a large prospective, randomized controlled trial, we assessed neurological function in patients with painful diabetic neuropathy (PDN) in response to 10 kHz spinal cord stimulation (SCS) [1,2]. In that study, we demonstrated that 10kHzSCS significantly improves innocuous and noxious sensory responses after 3 months. Here, we assessed the long term durability of these improvements over 24 months of continuous 10 kHz SCS.

Methods: Neurologists trained investigators to perform neurological examinations based on American Diabetes Association Standards of Care [3] on subjects implanted with a stimulator(n=154) at baseline, 3-, 6-, 12-, and 24-month visits. Innocuous and noxious sensory function was assessed by guided subject response to a 10 g monofilament and pinprick, respectively, at10 locations on each foot (Figure 1). Each response was categorized by the subject as either “Absent”, “Diminished”, “Normal”, or “Hypersensitive”.

Results: Neurological improvements of innocuous and noxious sensation after 3 months of10kHzSCS were durably maintained over 24 total months as results observed at 3 months with10kHzSCS were not statistically different at the 6-, 12, or 24-month time points (RM-ANOVA, Tukey pairwise comparison) (Figures 2 and 3). Also, all follow-up responses were significantly different from baseline (p <.001). Over the 3- to 24-month follow-up period, the number of mean “Normal” responses per patient from innocuous sensory testing increased from 3.3 at baseline to a range of 5.6-6.3 locations out of 20 (10 per foot). Additionally, the number of mean “Absent” responses decreased from 10.5 at baseline to 6.4-7.1 over the follow-up period. For noxious sensory testing, the number of mean “Normal” responses increased from 2.9 at baseline to a 6.3-7.1. Additionally, the number of mean “Absent” responses decreased from 8.7at baseline to 5.2-6.2 over subsequent time points. No mean “Hypersensitive” response of any group at any time point was greater than 1.0locations out 20.

Conclusion: Diabetic patients who received 10 kHz SCS demonstrated significantly increased “Normal” responses and reduced "Absent" responses across 20 different locations on their feet. These changes in responses are first apparent at the 3-month follow-up and are durable out to 2years. This return to normal tactile and nociceptive function has implications for potentially impeding progression of the diabetic disease state as well as common diabetic foot sequelae, such as foot ulcers.