Herpes zoster (HZ), also known as shingles, is caused by the varicella-zoster virus (VZV). Approximately 1/4 of the global population is affected by HZ, with statistics showing that about 90% of shingles patients experience acute neuralgia, and about 1/3 develop postherpetic neuralgia (PHN) after shingles. In PHN patients, about 30%-50% of the pain can persist for more than one year, and some cases can last for more than 10 years. PHN is a common complication of HZ characterized by intense pain in the area where the rash has healed, often described as burning, electric shock-like, or stabbing pain, severely affecting patients' sleep, emotions, work, and daily life. Additionally, approximately 43% of PHN patients exhibit symptoms of toxic anxiety or depression, significantly impacting their quality of life and increasing the societal burden. Due to the global aging population, the incidence of HZ and PHN is expected to significantly increase in the next 10 years, making effective prevention and treatment of PHN an urgent health issue. Although various treatments are available for PHN, a small number of patients remain unresponsive to multiple therapies, resulting in treatment-resistant chronic pain. The lack of a clear understanding of the underlying mechanisms contributes to the suboptimal treatment outcomes for PHN. Elastography, a technique that quantifies the mechanical properties of tissues by measuring their natural elasticity, trauma, degeneration, and healing processes, has shown promise as an innovative approach. Shear wave elastography (SWE) has been used to study the biomechanical characteristics of skeletal muscles by measuring the propagation speed of shear waves induced by ultrasound to quantify the shear elastic modulus, which characterizes the stiffness of soft tissues. In this study, the investigators intend to use elastography to observe the elasticity of muscle tissue in the lesions of PHN patients, with the unaffected side serving as a control. Elastography offers non-invasive, convenient, and straightforward advantages, further contributing to providing new directions for treatment and revealing the role of muscle tissue in PHN by offering new evidence. It also offers new treatment options and targets for PHN patients. While treatment of PHN is primarily focused on neural mechanisms due to HZ's neurotropism nature, recent evidence suggests that muscle tissues within the affected regions may also experience pathological changes, that contribute to the pain. These changes could reveal novel therapeutic targets and enhance patient prognosis. This study aims to investigate these muscular changes and explore myogenic pain mechanisms in PHN patients. It employs ultrasound elastography to compare muscle elasticity between the affected and unaffected sides and conduct muscle biopsies for pathophysiological analysis to uncover the underlying mechanisms.