The Efficacy of Superior Laryngeal Nerve Block for Chronic Cough: A Scoping Review

Chronic cough poses diagnostic and treatment challenges due to its often multifactorial nature. Chronic cough associated with laryngeal hypersensitivity is linked to sensory neuropathy of the superior laryngeal nerve and can be complex to manage. Superior laryngeal nerve (SLN) blocks are increasingly being utilized by laryngologists to treat refractory chronic cough with the intent of reducing inflammation and nerve hypersensitivity. This scoping review aims to provide an overview of the current literature examining the efficacy of SLN blocks for treatment of chronic cough, identify knowledge gaps, and guide future studies.

A search strategy was developed in collaboration with a medical librarian and run in Ovid Medline, Embase (Elsevier), Web of Science Core Collection (Clarivate), CINAHL Ultimate (Ebscohost), Cochrane, and Google Scholar (via Harzing's Publish or Perish). Search scope was from the inception of each database to March 5, 2024. Inclusion criteria were broad and focused on any study that utilized SLN block(s) for the treatment of chronic cough. The searches yielded 1264 articles that were loaded into Covidence systematic review software for deduplication and screening. Title and abstract and then full-text screening were performed.

Twelve studies met inclusion criteria. Study designs varied, including retrospective reviews, case series, and one placebo-controlled trial. Outcome measures included validated patient-reported cough-specific quality of life measures and/or subjective patient reports. The number of blocks primarily ranged from an average of 2-4 per patient, with follow-up durations ranging anywhere from 2 weeks to 22.5 months. Adverse effects were minimal and primarily self-limiting. Other reported interventions included behavioral cough suppression therapy, used in conjunction with SLN blocks, and neuromodulators, which were often trialed prior to SLN therapy. All 12 studies reported improvement in cough, and while several studies reported significant improvements in patient-reported outcomes using Cough Severity Index and Leicester Cough Questionnaire questionnaires, only eight studies provided statistical testing with P values. The remaining studies did not perform statistical analyses or report confidence intervals, instead presenting descriptive or qualitative results.

Literature on the efficacy of SLN blocks for chronic cough reveals consistent positive outcomes. There is a need for randomized controlled trials, systematic studies with larger cohorts, longitudinal follow-up, and further comparison of ipsilateral versus bilateral blocks to determine the efficacy of SLN blocks for treatment of chronic cough.