Symptom Control Effectiveness of Superior Laryngeal Nerve Block in Patients with Chronic Cough: A Systematic Review and Meta-Analysis.

Background and Objectives: To evaluate the efficacy of superior laryngeal nerve block (SLB) in the management of chronic cough associated with refractory laryngeal hypersensitivity. Materials and Methods: Studies assessing Cough Severity Index (CSI) changes before and after SLB or comparing SLB with sham interventions were included. Pooled analyses evaluated CSI reduction, subjective improvement, and adverse events. Results: Twelve studies involving 759 patients were analyzed. SLB significantly reduced CSI, and the improvement was maintained within the available follow-up period, with no difference between short-term (<100 days) and long-term (>100 days) follow-up (p = 0.5145). Most protocols used initial unilateral SLB with contralateral injection for non-responders, resulting in more than two blocks per patient on average. Subjective improvement occurred in 74%, with ≥50% CSI reduction in 55% and satisfactory response after a single block in 17%. No serious treatment-related adverse events were reported, although the available evidence was insufficient to exclude rare or delayed complications. Conclusions: SLB was associated with improvement in refractory chronic cough in predominantly uncontrolled observational studies. Although one small placebo-controlled trial suggested benefit over saline injection, the current evidence remains insufficient to establish definitive efficacy, and adequately powered placebo-controlled randomized controlled trials are needed to confirm its efficacy and durability.