Diffusion-weighted imaging of the dorsal root ganglion as a quantitative biomarker reflecting the severity and prognosis of herpes zoster：a prospective magnetic resonance imaging study

Abstract This prospective study aimed to characterize diffusion-weighted imaging (DWI) of the dorsal root ganglion (DRG) in herpes zoster (HZ) and to investigate the apparent diffusion coefficient (ADC) as a quantitative evaluation indicator for HZ as well as a predictor for postherpetic neuralgia (PHN). Thirty-six patients with HZ and ten healthy volunteers underwent magnetic resonance imaging (MRI) scanning. The ADC values of the affected and symmetric asymptomatic DRG were collected and compared. The rash intensity (RI), visual analog scale (VAS), pain index (PI), insomnia severity index (ISI), self-rated anxiety scale (SAS) and self-rated depression scale (SDS) were used to assess clinical characteristics. DWI analysis showed that ADC values of symptomatic DRG were significantly lower than those of symmetric asymptomatic DRG in both the HZ-period (P < 0.001) and the follow-up period (P < 0.001). The ADC value difference of the bilateral DRG at the affected segment (asymptomatic value – symptomatic value) was correlated with several clinical data in the HZ period. Analysis of the receiver operating characteristic curve revealed that the HZ-period ADC value difference had a high predictive value for PHN (Area under the curve = 0.815, P = 0.003). The cutoff value was 0.121 × 10 –3 mm 2 /s. DWI of the DRG can quantitatively display the change in the affected DRG in HZ patients and may indicate nerve necrosis and structural variation of the neuronal cell membrane. DWI of the DRG can help evaluate the clinical status of patients with HZ and may be a potential prognostic indicator for the occurrence of PHN.