Predicting outcome in peripheral nerve stimulation for chronic neuropathic pain.

ABSTRACT

OBJECTIVE: The aim of the study was to investigate the predictive value of percutaneous electrical nerve stimulation (PENS) in peripheral nerve stimulation (PNS) for chronic neuropathic pain. MATERIALS AND METHODS: Twelve patients being evaluated for PNS for chronic neuropathic pain were included in this survey. Stimulation with acupuncture needles was applied with continuous high frequency stimulation. Position, polarity, frequency and amperage threshold of perception, and adverse effects were noted. Additional stimulation side effects were documented. A StimScore was developed to evaluate effects in a standardized manner. This StimScore comprises coverage of the painful area, therapeutic range, and amperage required for successful stimulation. StimScore was determined during PENS, during test stimulation, and under final stimulation. RESULTS: PNS was well tolerated by all patients. Seven of the 12 patients (58%) were classified as successfully treated, and 5/12 patients (42%) as unsuccessful. The mean overall pain reduction in the first group was 4.0 points (SD = 2.87, P = 0.010) and 2.4 points (SD = 1.29, P = 0.014), respectively, on the visual analogue scale. In the successful stimulation group, a mean StimScore of 13.14 (SD 11.19-15.0) was calculated vs. 10.4 (95% CI 8.52-12.28) in the unsuccessful stimulation group (P = 0.033, 95% CI = 0.265-5.220). CONCLUSIONS: Predicting response to PNS is crucial to reduce the number of patients implanted in vain. To adopt PENS via electroacupuncture needles as a percutaneous simulation method for PNS seemed to be feasible. The technique presented herein bears the potential to improve patient selection combined with reduced invasiveness. The presented results are encouraging and deliver a starting point for further trials.