Are vagus nerve stimulators (VNS) effective?

From the Guidelines

Vagus nerve stimulators (VNS) are a viable treatment option for certain conditions, particularly drug-resistant epilepsy, with approximately 51% of patients experiencing a 50% or greater reduction in seizure frequency 1.

Key Points

• VNS involves implanting a pulse generator in the chest that sends electrical impulses to the vagus nerve through a wire wrapped around the nerve in the neck.
• The standard stimulation protocol typically involves intermittent stimulation (30 seconds on, 5 minutes off) at frequencies of 20-30 Hz.
• Higher amplitudes, when used in combination with higher duty cycle, higher frequency, and longer pulse widths, have been shown to be more efficacious in reducing seizure frequency 1.
• Side effects are generally mild and include hoarseness, cough, or throat discomfort during stimulation.
• VNS works by modulating brain activity through the vagus nerve's extensive connections to key brain regions involved in seizure generation and mood regulation.

Evidence-Based Recommendation

Based on the most recent and highest quality study, VNS is recommended for patients with drug-resistant epilepsy who have not responded adequately to medications, with the goal of reducing seizure frequency and improving quality of life 1.

Important Considerations

• The therapy requires surgical implantation under general anesthesia and regular follow-up appointments for device adjustments.
• While not effective for everyone, VNS offers a valuable option for patients who haven't responded adequately to medications, with benefits potentially increasing over months to years of use.
• The selection of VNS parameters is crucial, and higher stimulation parameters have been shown to be more effective in reducing seizure frequency 1.

From the Research

Efficacy of Vagus Nerve Stimulation

• Vagus nerve stimulation (VNS) has been consistently demonstrated to be effective in treating epilepsy, with approximately 50% of patients experiencing at least 50% reduced seizure frequency after 2 years 2.
• VNS has also been shown to be effective in treating depression, with studies suggesting that it can lead to an improvement of about 25-35% in depression scores 3.
• The efficacy of VNS on seizure frequency has been demonstrated in both children and adults, in lesional and non-lesional cases, in focal and generalized epilepsies, and on both seizures and epilepsy comorbidities 3.

Mechanism of Action and Safety

• The mechanism of action of VNS is not fully understood, but it is thought to involve the stimulation of afferent vagal brainstem pathways associated with mood regulation 4.
• VNS has been shown to be safe, with rare adverse events including surgical adverse events and stimulation side effects such as hoarseness, voice change, and cough 2.
• Non-invasive VNS devices have been found to be safer, but their efficacy is limited due to the scarcity of large cohort studies and the disparity of methodological approaches 3.

Clinical Applications

• VNS is currently the only FDA-approved neurostimulation treatment for severe treatment-resistant depression (TRD) 4.
• VNS has been shown to be beneficial in improving quality of life and suicidality among unipolar TRD patients and depression among bipolar TRD patients 4.
• Ongoing and future studies continue to investigate the psychiatric benefits of VNS within the TRD population 4.