Object: Postherpetic neuralgia (PHN) is pain that persists for 1-3 months after herpes zoster onset. It is the most common complication of herpes zoster and occurs in 15-40% of patients with herpes zoster. PHN has been suggested to be related with the lesion of doral root ganglion (DRG). However, the studies are almost limited to autopsies and animals , and the mechanism of PHN is still unclear. This study was conducted to investigate morphological and metabolic changes of DRG and sympathetic ganglion in patients with postherpetic neuralgia on MRI. Method: 30 patients diagnosed as PHN were recruited. The volume and fractional anisotropy of DRG of lesion dermatomes were measured under MRI, and compared with contralateral and adjacent DRG. The volume and fractional anisotropy of sympathetic ganglion of lesion dermatomes were also measured under MRI, and compared with contralateral and adjacent sympathetic ganglion.Then, the association between clinical phenotypes and DRG changes were analyzed.