A critical review published in the Journal of Translational Gastroenterology has assessed the clinical effectiveness and safety of electrical stimulation of cranial nerves for treating dysphagia, a common comorbidity of neurological diseases. The review included implantable, minimally invasive, and non-invasive approaches, following PRISMA guidelines, and analyzed 15 clinical studies.
The review included 4 studies on vagus nerve stimulation (VNS) and 11 on pharyngeal electrical stimulation (PES). PES and transcutaneous VNS (taVNS and tcVNS) showed beneficial effects on validated dysphagia outcome measures. No long-term severe adverse effects were reported.
Results: VNS Studies
- tcVNS (1 mA) in stroke patients: Significant improvements in Standard Swallowing Scale and Functional Communication Measure.
- taVNS in stroke: Significant improvement in Functional Communication Measure.
- icVNS in multiple sclerosis (n=3): No statistical assessment; no severe adverse events.
- VNS protocols were heterogeneous (e.g., DC vs. pulsed, different frequencies and sites).
Results: PES Studies
- Eleven studies used a nasogastric catheter with ring electrodes (5 Hz, 200 µs, 20–30 mA, 10 min/day, 3 days).
- Significant reduction in Penetration-Aspiration Scale (PAS) in multiple studies.
- Reduced dysphagia incidence and reintubation rates.
- One case of chest sepsis related to catheter insertion, not stimulation.
- PES has FDA de novo clearance for short-term treatment of dysphagia in stroke patients.
Discussion
- Evidence for PES, taVNS, and tcVNS is converging; evidence for icVNS is preliminary.
- Approaches target different pathways: PES targets afferents via CN IX and pharyngeal CN X; tcVNS/icVNS targets the main vagal trunk; taVNS targets the auricular branch.
- PES: FDA-cleared, invasive, resource-intensive, suitable for short-term hospital use.
- taVNS/tcVNS: Non-invasive, low-cost, suitable for home use, not yet FDA-approved for dysphagia.
- icVNS: Potential for adherence but high cost, surgical risks, and unconfirmed effectiveness.
Limitations
- Single database search, exclusion of non-English studies, single-author analysis.
- VNS studies had methodological heterogeneity; meta-analysis was not possible.
- Findings may not generalize to esophageal dysphagia.
Conclusions
Cranial nerve stimulation, particularly PES and transcutaneous VNS, shows promise for treating oropharyngeal dysphagia. The approaches are complementary, with PES suited for acute hospital settings and transcutaneous VNS for outpatient or home use. PES is FDA-cleared for short-term stroke-related dysphagia; transcutaneous VNS requires further trials.