Noninvasive vagus nerve stimulation in otolaryngology: A scoping review and evidence map.

Background

Noninvasive vagus nerve stimulation (nVNS) may influence brainstem nuclei and ascending networks via vagal afferent pathways and has been investigated as an additional treatment for otolaryngological problems. Nonetheless, the evidence base is fragmented and methodologically diverse.

Objective

To conduct a comprehensive review with evidence mapping to map and synthesize reported human clinical evidence on nVNS in otolaryngology and identify gaps for future studies.

Methods

A scoping review guided by PRISMA-ScR was conducted in the PubMed, Embase, Web of Science, and Scopus databases from inception to December 20, 2025. Eligible designs included randomized and nonrandomized interventional trials, cohort and mechanistic analyses, and case series. Data were organized using a predefined otolaryngology outcome-domain framework and presented as an evidence map.

Results

Of 4974 records, 2690 unique records were screened, and 20 studies were included. Seven indication categories were represented: pharyngeal dysesthesia (n = 1), laryngopharyngeal reflux-related disorders (n = 1), MD (n = 2), olfactory dysfunction (n = 2), dysphagia (n = 3), vestibular disorders/vestibular rehabilitation (n = 3), and tinnitus (n = 8). Outcomes were primarily patient-reported, with selected objective functional and mechanistic measures. Common limitations included small samples, variable comparators and blinding strategies, non-harmonized stimulation parameters and treatment-course definitions, short follow-up, and heterogeneous reporting of harms.

Conclusions

Current evidence on otolaryngologic nVNS is largely exploratory and should not be interpreted as establishing clinical effectiveness. Tinnitus constitutes the largest evidence cluster, whereas vestibular rehabilitation and dysphagia studies more often incorporate operationalizable functional endpoints. Future confirmatory trials should harmonize stimulation and reporting, strengthen sham-controlled blinding, prespecify phenotype and mechanistic anchors, and extend follow-up to assess durability and maintenance.