Dysphagia, a severe comorbidity of many neurological diseases, often lacks targeted therapies. This critical review assessed the clinical effectiveness and safety of electrical stimulation of cranial nerves for treating dysphagia, including implantable (direct nerve stimulation), minimally invasive (pharyngeal electrical stimulation, PES), and non‑invasive (transcutaneous) approaches. Following PRISMA guidelines, 15 clinical studies were included: four on vagus nerve stimulation (VNS; implantable and transcutaneous) and eleven on PES. Most evaluated studies, particularly for PES and transcutaneous VNS, demonstrated significant beneficial effects on validated dysphagia outcome measures. Importantly, no long‑term severe adverse effects were reported. Cumulative evidence indicates that VNS and PES can effectively alleviate dysphagia symptoms. The different approaches appear complementary, with distinct profiles suitable for different therapeutic contexts (e.g., short‑term hospital‑based vs. long‑term at‑home treatment), offering valuable options for individualized dysphagia therapy.
Introduction
Dysphagia affects up to 87% of Parkinson's patients, 31–68% of post‑stroke patients, and 31% of healthy elderly individuals. It leads to malnutrition, dehydration, and aspiration pneumonia. Oropharyngeal dysphagia involves difficulty initiating swallowing; it results from impaired sensorimotor coordination of cranial nerves (CN) V, VII, IX, X, and XII. Standard care relies on swallowing exercises, which can be slow and ineffective. Electrical stimulation of cranial nerves offers a novel approach to restore or enhance this coordination. This review critically assesses four approaches: implantable cervical VNS (icVNS), transcutaneous auricular VNS (taVNS), transcutaneous cervical VNS (tcVNS), and pharyngeal electrical stimulation (PES).
Methods
A systematic search of PubMed (up to November 2025) was conducted following PRISMA guidelines. Inclusion criteria: English language, full‑text availability, statistical results (with pragmatic exception for icVNS due to small sample sizes). Animal studies, reviews, abstracts, and case reports were excluded. Risk of bias was assessed using the modified Newcastle‑Ottawa Scale (NOS). Fifteen clinical studies (four VNS, eleven PES) were included.
Results – VNS Studies
Four VNS studies were identified (Table 3):
tcVNS (DC, 1 mA) in stroke (two studies): significant improvements in Standard Swallowing Scale (Δ –8.1 ± 4.2, p<0.001) and Functional Communication Measure (Δ 3.05 ± 0.50, p<0.001).
taVNS (25 Hz, 0.5 ms, 1.5–2.0 mA) in stroke: significant FCM improvement (p<0.001).
icVNS (10 Hz, 1.25 mA) in multiple sclerosis (n=3): no statistical assessment; no severe adverse events.
All VNS studies reported no severe adverse events. However, VNS protocols were highly heterogeneous (DC vs. pulsed, different frequencies, sites), limiting interpretability.
Results – PES Studies
Eleven PES studies (Table 4) demonstrated high homogeneity: all used a nasogastric catheter with ring electrodes at 5 Hz, 200 µs, 20–30 mA for 10 minutes daily over 3 days.
Significant reduction in Penetration‑Aspiration Scale (PAS) in multiple studies (e.g., Δ –1.5 ± 1.5, p<0.05; Δ –3.3 ± 0.8, p<0.01).
Reduced dysphagia incidence (PAS ≥3) and reintubation rates (e.g., 24% reduction, p<0.001).
One case of chest sepsis related to catheter insertion, not stimulation itself.
PES has FDA de novo clearance for short‑term treatment of dysphagia in stroke patients.
Discussion
The principal finding is converging evidence for effectiveness and safety of PES, taVNS, and tcVNS; evidence for icVNS remains preliminary. These approaches are not interchangeable due to distinct mechanisms:
PES targets afferent pathways (CN IX and pharyngeal CN X) in the oropharyngeal mucosa, rapidly restoring brainstem swallowing reflexes. Its niche is acute/subacute hospital settings, including ICU patients.
tcVNS/icVNS targets the main vagal trunk (mixed sensory/motor), driving longer‑term cortical and brainstem plasticity.
taVNS targets the auricular branch (pure sensory, projecting to the nucleus tractus solitarius), analogous to PES in mechanism.
Clinical profiles (Table 5):
PES: Confirmed effectiveness, FDA‑cleared, but invasive (nasogastric catheter), resource‑intensive, unsuitable for home use. Niche: short‑term hospital‑based severe dysphagia.
taVNS/tcVNS: Non‑invasive, inexpensive, suitable for home use, but not yet FDA‑cleared for dysphagia. Niche: outpatient/home setting for mild‑to‑moderate dysphagia.
icVNS: "Implant and forget" potential for high adherence, but high cost, surgical risks, and unconfirmed effectiveness. Niche: currently non‑viable.
Limitations
Single database (PubMed), exclusion of non‑English studies, single‑author analysis (risk of bias). VNS studies suffer from methodological heterogeneity; meta‑analysis not feasible. All studies focused on oropharyngeal dysphagia; findings may not generalize to esophageal dysphagia.
Conclusions
CN stimulation, particularly PES and transcutaneous VNS, holds significant promise for treating oropharyngeal dysphagia. These approaches are complementary rather than competitive, with distinct profiles suiting different clinical contexts (hospital vs. home, acute vs. long‑term). PES is FDA‑cleared for short‑term stroke‑related dysphagia; transcutaneous VNS requires further large‑scale trials for regulatory approval. Future research should standardize protocols, conduct larger randomized trials, and explore applications across diverse patient populations.
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The study was recently published in the Journal of Translational Gastroenterology .
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