Effect of Erector Spinae Plane Block Applied to Painful Herpes Zoster Patients Who Failed to Respond to Pregabalin Treatment on Immunological Marker Levels and Postherpetic Neuralgia Incidence Rate.

Purpose: Postherpetic neuralgia (PHN) is one of the most debilitating complications of herpes zoster and represents a major cause of chronic neuropathic pain. Increasing evidence suggests that immune dysregulation plays a critical role in neuropathic pain development. This study aimed to investigate the effects of the erector spinae plane (ESP) block on PHN development and immunological marker levels in herpes zoster patients who did not respond to pregabalin therapy. Patients and Methods: This prospective, controlled, single‑blind, non-randomized study included 30 patients with herpes zoster. Pregabalin therapy was initiated in all patients. Patients whose pain was adequately controlled with pregabalin were assigned to Group I, whereas patients with insufficient pain control received an ESP block and were assigned to Group II. Blood samples were collected at baseline, after treatment response, and at the three-month follow-up. T‑cell subsets and natural killer (NK) cell subgroups were analyzed using flow cytometry. Pain intensity, sleep interference, and PHN incidence were evaluated during follow-up. Results: Pain and sleep interference scores improved significantly over time in both groups (P < 0.05).The incidence of PHN did not differ significantly between the groups. However, at the three-month follow-up, patients in the ESP block group, who were receiving higher pregabalin doses, demonstrated lower CD3⁺ and CD4⁺ T-cell levels and reduced NK cell subset levels compared with Group I (P < 0.05).Baseline NK CD56 Bright levels were significantly higher in patients who did not develop PHN (P < 0.05). Conclusion: Although the ESP block did not reduce the incidence of PHN, immunological differences were observed between the treatment groups during follow-up. Higher baseline NK CD56 Bright levels in patients who did not develop PHN suggest a potential protective association between preserved NK-cell-mediated immunity and resistance to pain chronification following herpes zoster.