Altered functional connectivity density in patients with herpes zoster and postherpetic neuralgia

Purpose: The aim of this study was to explore intrinsic functional connectivity patterns in patients with herpes zoster (HZ) and postherpetic neuralgia (PHN). Patients and methods: Thirty-three right-handed HZ patients (13 males; mean age 57.15 +/- 9.30 years), 22 right-handed PHN patients (9 males; mean age 66.13 +/- 6.77 years), and 28 well-matched healthy controls (HC) (9 males; mean age 54.21 +/- 7.72 years) underwent resting-state functional magnetic resonance imaging for intrinsic functional connectivity analyses. Functional connectivity density (FCD) was calculated and compared among the PHN, HZ, and HC groups. In addition, the Pearson correlation coefficient was calculated to compare various clinical indices in the regions with abnormal FCD values. Results: Compared with the HC, both HZ and PHN patients showed significantly decreased FCD in the precuneus, and patients with HZ displayed significantly increased FCD in the brainstem/limbic lobe/parahippocampalgyrus, whereas patients with PHN displayed significantly increased FCD in the hippocampus (correlation thresholds r=0.25, voxel level of P<0.01 and Gaussian random field theory at a cluster level of P<0.05). However, the FCD was not significantly different between the PHN and HZ patients. Furthermore, the decreased FCD in the precuneus was positively correlated with the visual analog scale score in the PHN group (r=0.672; P=0.001). Conclusion: Decreased connectivity of the precuneus occurred in both HZ and PHN patients, indicating a disrupted default-mode network. Furthermore, in the HZ group (initial stage of the virus infection), hyperconnectivity was observed in systems involved in pain transmission and interpretation, but hyperconnectivity only occurred in the hippocampus in the PHN group (neuropathic pain stage).