Background: Conventional treatment for painful peripheral diabetic neuropathy is largely symptomatic and often ineffective, with unacceptable side-effects. We tested electrical spinal-cord stimulation for the management of chronic neuropathic pain.
Methods: Ten diabetic patients who did not respond to conventional treatment (mean age 51 [SD 9.3] years, six with type II diabetes, mean duration of diabetes 12 [6.3] years, mean duration of neuropathy 5 [2.1] years) were studied. The electrode was implanted in the thoracic/lumbar epidural space. Immediate neuropathic pain relief was assessed by visual analogue scale (VAS) after connecting the electrode, in a random order, to a percutaneous electrical stimulator or to a placebo stimulator. Exercise tolerance was assessed on a treadmill.
Findings: Eight subjects had statistically significant pain relief with the electrical stimulator (p < 0.02) and were therefore converted to a permanent system. Statistically significant relief of both background and peak neuropathic pain was achieved at 3 months (n = 7, p = 0.016), at 6 months (n = 7, p = 0.03), and at the end of the study (14 months, n = 7, background pain p = 0.06, peak pain p = 0.03). One patient died 2 months after the start of the study of unrelated cause while continuing to benefit from treatment and another patient ceased to benefit at 4 months. McGill pain questionnaire scores with the stimulator turned off did not change significantly from baseline scores, indicating that the severity of the underlying pain was unaltered. However, with the stimulator turned on, there was a statistically significant (p < 0.05) improvement in all four components of the score, by the end of the study. At the end of the study, six patients continued to gain significant pain relief and used the stimulator as the sole treatment for their neuropathic pain. For example, median background and peak pain scores at the end of study, were, respectively, 77 and 81 with the stimulator off and 23 and 20 with the stimulator on. Exercise tolerance significantly improved at 3 months (n = 7, median % increase 85 [IQR, 62-360], p = 0.015) and at 6 months (n = 6, 163 [61-425], p = 0.0007). Electrophysiological tests, vibration perception-threshold, and glycaemic control were unchanged.
Interpretation: Electrical spinal-cord stimulation offers a new and effective way of relieving chronic diabetic neuropathic pain and improves exercise tolerance. The technique should be considered in patients with neuropathic pain who do not respond to conventional treatment.