Alterations in local activity and functional connectivity in patients with postherpetic neuralgia after short-term spinal cord stimulation

Abstract

Introduction: The efficacy of short-term spinal cord stimulation (stSCS) as a treatment for neuropathic pain in patients with postherpetic neuralgia (PHN) has already been validated. However, the potential alterations in brain functionality that are induced by such treatment have yet to be completely elucidated.

Methods: This study use resting-state functional magnetic resonance imaging (rs-fMRI) to detect the changes in regional homogeneity (ReHo) and degree centrality (DC) related to stimulator-induced pain relief in patients with PHN. A total of 10 patients with PHN underwent an MRI protocol at baseline and after stSCS. Alterations in ReHo and DC were then compared between baseline and after stSCS. We investigated the relationship between clinical parameters and functional changes in the brain.

Results: Clinical parameters on pain, emotion, and sleep quality were correlated with ReHo and DC. ReHo and DC were significantly altered in the middle temporal gyrus, precuneus, superior frontal gyrus, supramarginal gyrus, inferior parietal lobule, rolandic operculum, middle occipital gyrus, superior parietal gyrus, and the precentral gyrus after stSCS. A significant correlation was detected between ReHo changes in the middle occipital gyrus, precuneus, inferior parietal gyrus, and changes in pain, emotion, and sleep quality. A significant negative correlation was detected between DC changes in the middle temporal gyrus, rolandic operculum, supramarginal gyrus, precuneus, inferior parietal gyrus, and changes in pain, emotion, and sleep quality.

Conclusion: This study found that stSCS is able to induce ReHo and DC changes in patients with PHN, thus suggesting that stSCS can change brain function to alleviate pain, sleep, and emotional disorder.

Keywords: emotion; functional magnetic resonance imaging; mechanisms of action; pain; postherpetic neuralgia; spinal cord stimulation.

Figure 1

Study protocol. Patients with PHN were enrolled prior to the implantation of the SCS and were followed up after the removal of the stSCS. Each patient underwent a neuroimaging protocol prior to SCS and 14 days after SCS. SCS, spinal cord stimulation; stSCS, short-time spinal cord stimulation; V, visit.

Figure 2

Boxplots for the clinical outcomes for all patients at baseline (in green) and after stSCS (in orange). The beginning four boxplots represent the four subscale scores of the SF-MPQ-2 (continuous pain, intermittent pain, predominantly neuropathic pain, and affective descriptors). The last two boxplots represent the two subscale scores for the HADS (HADS-A and HADS-D). NRS, numeric rating scale; PSQI, Pittsburgh sleep quality index; SCS, spinal cord stimulation. *p < 0.05.

Figure 3

Significant differences in ReHo between baseline and after stSCS in axial and sagittal slices. The warm colors indicate a higher ReHo value whereas the cooler colors indicate a lower ReHo value at baseline and after stSCS (p < 0.05). Brain images are displayed in radiology convention (the left of the figure represents the right side of the patient's brain and vice versa).

Figure 4

Significant differences in DC between baseline and after stSCS in axial and sagittal slices. The warm colors indicate higher DC values at baseline and after stSCS (p < 0.05). Brain images are presented in radiology convention (the left of the figure represents the right side of the patient's brain and vice versa).