American Society for Peripheral Nerve

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Does Duration of Neuropathy, Duration of Diabetes, or HbA1c Affect the Response to Nerve Decompression in Diabetic Neuropathy: Conclusions from the DNND (Diabetic Neuropathy Nerve Decompression) Study – a Prospective, Randomized, Controlled Trial
Austin Hembd, MD1; Gil Wolfe, MD2; Philip Raskin, MD1; Steven Vernino, MD1; So-Youn Park, MS1; Shai Michael Rozen, MD1
1UT Southwestern Medical Center, Dallas, TX, 2Buffalo General Medical Center, Buffalo, NY

Introduction: The DNND study - a level one prospective, randomized, double blinded, sham-procedure controlled trial, was designed to evaluate the effects of nerve decompression on pain reduction in patients suffering from painful diabetic neuropathy (PDN). In an average 54.5-month follow–up, the seven-year study revealed a statistical reduction in pain in the surgical vs. non-surgical group (SD=2.54;p<0.0001) and surgical versus sham group (7.47+2.09 vs. 5.97+2.43, p=0.0002). Yet, the effect of HbA1c, duration of diabetes, and duration of neuropathy on pain reduction after nerve decompression has not been elucidated. This study aims to analyze if these three variables affect the pain reduction over time in patients after nerve decompression.

Methods: Of the 2987 screened patients in the DNND study, statistics were based on the 138 enrolled patients, with 92 randomized to surgery and 46 as controls. At average follow-up period of 54.5 months, 36 surgical patients (each having a side randomized to nerve decompression or sham-procedure), and 14 control patients had full completion data. The significant reductions in pain scores at the 1 and 4-year follow-ups in the surgical and sham-procedure legs when compared to the non-surgical legs had previously been established. The variables: 1) duration of diabetes, 2) duration of neuropathy, and 3) HbA1c level were modeled with the pain scores, and analysis was completed via Analysis of Variance (ANOVA) models by the UT Southwestern Department of Biostatistics.

Results: There was no statistically significant impact on the pain scores at baseline, 1-year, or 54.5 month follow-ups by HbA1c levels (F-value=. 15, P< .69), the duration of neuropathy (F-Value=.02, P<.88), nor the duration of diabetes (F-Value= .45, p<.71) in the 50 patients who had full 54.5 month follow-up data.

Conclusion: The seven-year clinical trial on which this analysis has been completed has substantial implications on the treatment and management of lower extremity diabetic neuropathy. However, it is crucial to first stratify which patients will have the best chance for benefit from surgical decompression. These results indicate that the efficacy of lower extremity nerve decompression for painful diabetic neuropathy is applicable across the broad spectrum of patients with varying severities and durations of diabetes.

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