What is the strength of evidence for transcutaneous cervical Vagal (Vagus) nerve stimulation?

From the Guidelines

The evidence for transcutaneous cervical vagal nerve stimulation (tcVNS) is moderate and growing, with most robust support for its use in treating episodic and chronic migraine, cluster headache, and certain types of depression. Clinical trials have demonstrated that tcVNS devices can reduce the frequency of migraine attacks by 25-40% when used regularly, typically for 2-minute stimulations applied to the neck 2-3 times daily 1. For acute migraine treatment, tcVNS may provide relief within 30-60 minutes. The evidence is less established but promising for conditions like epilepsy, inflammatory disorders, and anxiety.

Key Findings

• The mechanism involves stimulation of the vagus nerve through the skin of the neck, which modulates neural pathways involved in pain processing, inflammation, and mood regulation by affecting neurotransmitter release and neuronal activity in the brain.
• Side effects are generally mild and include skin irritation, voice changes, and muscle contractions during stimulation.
• While tcVNS shows promise as a non-pharmacological intervention with minimal side effects, it should be considered as part of a comprehensive treatment approach rather than a standalone therapy for most conditions.
• A recent study published in the European Respiratory Review in 2021 found that transcutaneous hypoglossal nerve stimulation (which is similar to tcVNS) showed statistically significant effects favoring the intervention in terms of quality of life, but not in terms of sleep efficiency or sleepiness 1.

Recommendations

• tcVNS should be considered as a treatment option for patients with episodic and chronic migraine, cluster headache, and certain types of depression, particularly those who have not responded to other treatments or have contraindications to traditional therapies.
• Further research is needed to fully establish the efficacy and safety of tcVNS for other conditions, such as epilepsy, inflammatory disorders, and anxiety.
• Patients should be closely monitored for potential side effects and adjustments made to the treatment protocol as needed.

From the Research

Strength of Evidence for Transcutaneous Cervical Vagal Nerve Stimulation

The evidence for transcutaneous cervical vagal nerve stimulation is based on several studies that have investigated its effectiveness and feasibility in various conditions, including epilepsy, depression, and traumatic brain injury.

• The study by 2 provides an overview of transcutaneous vagus nerve stimulation, highlighting its potential as a non-invasive alternative to invasive cervical vagus nerve stimulation.
• Another study by 3 used fMRI to investigate whether afferent vagal projections can be accessed non-invasively by transcutaneous electrical stimulation of the antero-lateral surface of the neck, and found that it can activate primary vagal projections in the brainstem and forebrain.

Therapeutic Applications

The therapeutic applications of transcutaneous cervical vagal nerve stimulation are diverse and include:

• Treatment of medication-refractory epilepsies, depressive mood disorders, headaches, and pain 2
• Improvement of cognitive and motor function after stroke 4
• Treatment of traumatic brain injury with cognitive dysfunction 4
• Treatment of treatment-resistant depression 5

Feasibility and Safety

The feasibility and safety of transcutaneous cervical vagal nerve stimulation have been investigated in several studies, including:

• A study by 6 that found that transcutaneous cervical vagal nerve stimulation can be effectively delivered in a remote setting, such as the home, with high accuracy and precision.
• A study by 4 that found that daily half-hour vagus nerve magnetic stimulation for ten days was feasible in patients with traumatic brain injury, with minimal side effects and no clinically significant effects on physiological parameters.
• A study by 5 that found that transcutaneous vagal nerve stimulation was feasible and well-tolerated in patients with treatment-resistant depression, with a compliance rate of 80% and few side effects.

Limitations and Future Directions

While the evidence for transcutaneous cervical vagal nerve stimulation is promising, there are limitations and future directions to consider, including:

• The need for further controlled studies to establish the efficacy of transcutaneous cervical vagal nerve stimulation in various conditions 3, 4, 5
• The need to optimize stimulation parameters and algorithms to improve treatment outcomes 2
• The need to investigate the long-term effects and potential side effects of transcutaneous cervical vagal nerve stimulation 5