Dorsal Root Ganglion Stimulation Relieves Chronic Neuropathic Pain Along With a Decrease in Cortical γ Power

Stimulation of dorsal root ganglion (DRG) is an ideal neuromodulative intervention, providing pain relief in localized chronic pain conditions because γ-band oscillations reflect the intensity of ongoing chronic pain in patients affected.

We aimed to observe the role of cortical γ-band power associated with the relief of chronic neuropathic pain through DRG stimulation (DRGS).

We examined nine patients (two women, mean age 56.8 years; range, 36-77 years) diagnosed with chronic neuropathic pain who underwent DRGS therapy. We used the numeric rating scale (NRS) on the painful limb and simultaneously recorded the electroencephalography to assess the broadband γ power. Assessments were conducted on the first day and on the seventh day after implantation of the DRGS system and then compared and correlated with the results of the NRS.

The NRS scores showed a significant decrease from the first day to the seventh day (p = 0.007). The resting-state γ power revealed a significant decrease (p = 0.021) between 30 and 45 Hz, recorded through the central electrode contralateral to the painful limb from the first day (mean [M] = 0.46, SD = 0.25) to the seventh day (M = 0.31, SD = 0.12) after DRGS. There was no significant change in the resting-state γ-band power recorded through the central electrode ipsilateral to the painful limb. However, we found a positive correlation in the γ-band power (r_s = 0.628, p = 0.005) with the NRS rating.

A lateralized decrease in broadband γ power may be considered further evidence supporting a reduction in the hyperexcitability of the nociceptive system in response to DRGS therapy. In the future, γ-band power could serve as a biomarker for assessing the efficacy of DRGS during the seven-day test phase preceding the implantation of the DRGS system.