Restoration of Laser Evoked Potentials (LEP) in Patients Receiving Dorsal Root Ganglion (DRG) Stimulation

Introduction: Chronic localized neuropathic pain represents a medical condition of difficult treatment. Recently, a novel target for neuromodulation, i.e., stimulation of the dorsal root ganglion (DRGS), has been shown effective in the management of neuropathic pain. However, the mechanisms underlying the effects of DRG stimulation are not well established.

Objectives: Based on this, the main goal of the present study was to evaluate the effects of DRG stimulation on pain intensity, and to associate these findings with alterations of pain cortical processing as measured by laser evoked potentials (LEP).

Methods: We analysed prospectively 12 patients implanted with a DRG stimulator (Spinal Modulation, Inc., Menlo Park, CA, USA) to manage chronic unilateral neuropathic pain. LEP assessment was performed with DRG stimulation in ON and OFF phases. The corresponding contralateral healthy region served as control. The measurements were performed at the baseline (T0), after one month in ON phase (T1), and after six months (T2). Pain intensity was assessed by Numerical Rating Scale (NRS). The questionnaires PDI, BPI, NPSI, PainDetect and SF-36 were also spplied.

Results: We observed a drastically pain reduction from NRS 8.4 ± 0.48 to 2.4 ± 1.49 during DRG stimulation at 6 months (p < 0.05, Mann-Whitney U-Test). N2/P2 peak-to-peak LEP amplitude was restored in ON: 4.45 ± 3.64 (T0) to 10.96 ± 4.19 (T2) at 6 months (p < 0.05).

Conclusions: DRG stimulation is an effective method to relieve chronic localized neuropathic pain. Restoration of the LEPs were related to better clinical outcome. Our data suggests that DRG stimulation can induce plastic changes in pain processing at cortical level.