Efficacy and safety of interferon-alpha 1b injection into the intervertebral foramen with ultrasonic guidance in patients with postherpetic neuralgia: study protocol for a randomized, double-blind, placebo-controlled, multicenter clinical trial - Hu, Hui-Min; Liu, Wen-Hui; Li, Chen; Shi, Qing; Liu, Chun-Hua; Liu, An-Xiang; Li, Yi-Fan; Zhang, Yi; Mao, Peng; Fan, Bi-Fa (Frontiers in Neurology, 2025)