Vagus Nerve Stimulation Side Effects: Risks 2025

Understanding Implanted Vagus Nerve Stimulation Side Effects: What You Need to Know

Implanted Vagus Nerve Stimulation Side Effects range from mild and temporary to serious complications. For patients considering or currently using implanted VNS therapy, understanding these potential risks is crucial for making informed treatment decisions and managing the therapy effectively.  Non implanted vagus nerve stimulators ( or non invasive vagus nerve stimulators )  carry almost none of the risks listed below 

Most Common VNS Side Effects:

• Voice changes (hoarseness, voice alteration) – 35.5% of patients
• Throat pain and discomfort – 12.9% of patients
• Coughing – 13.9% of patients
• Shortness of breath during stimulation
• Tingling sensations (paresthesias) in the neck area

Surgical Risks:

• Postoperative infection – approximately 3% of patients
• Vocal cord paralysis – 1.4% of patients
• Bleeding (hematoma) – 1.9% of patients
• Device malfunction requiring replacement surgery

Serious but Rare Side Effects:

• Cardiac complications (bradycardia, very rare cardiac arrest)
• Permanent vocal cord damage
• Sleep apnea (new onset or worsening)
• Aspiration pneumonia

Many common side effects diminish over time as the body adapts. Notably, cognitive side effects often seen with epilepsy medications are not reported with VNS therapy.

Peter Staats, a board-certified Anesthesiologist and neuromodulation specialist, states, “Understanding Vagus Nerve Stimulation Side Effects helps patients make confident treatment decisions and manage their therapy effectively… proper patient education about potential risks leads to better outcomes and improved quality of life.”

Simple Vagus Nerve Stimulation Side Effects word guide:

• Living with VNS
• VNS pulse width
• Vagus Nerve Stimulation (VNS)

Implanted Vagus Nerve Stimulation (VNS) therapy is an established neuromodulation technique used for refractory epilepsy, depression,  stroke recovery and has recently been approved for rheumatoid arthritis. It involves implanting a small device that sends mild electrical pulses to the vagus nerve. While effective, it’s important to be aware of the potential Vagus Nerve Stimulation Side Effects. This guide provides a comprehensive overview of common and rare side effects, their management, and key considerations before implantation.

Surgical Risks and Post-Operative Complications of VNS Implantation

VNS therapy begins with a surgical procedure. While generally safe, it’s important to understand the potential complications.

The VNS implantation surgery takes 45 to 90 minutes. A surgeon places a small pulse generator under the skin in the upper chest and connects a thin wire to the left vagus nerve in the neck. Most patients go home the same day, but some may stay overnight for observation.

Postoperative infections occur in about 3% of patients. Most clear up with antibiotics, but in rare cases, the device may need to be temporarily removed. Swelling and pain at the incision sites are normal and typically fade within a few weeks.

Lower facial weakness was more common with early VNS devices; modern techniques have reduced this risk to just 0.2% of cases. Similarly, electrode lead breaks are much less common now due to improved technology.

For more detailed information about these concerns, you can explore VNS Therapy Complications.

Risks Directly from the Surgical Procedure

Every surgery has risks. Anesthesia risks include allergic reactions or breathing problems. The most common post-surgical concern is surgical site infection. Your team will provide instructions on keeping incisions clean. Watch for increased redness, warmth, or unusual drainage.

Hematoma (bleeding under the skin) occurs in about 1.9% of patients and usually resolves on its own. Nerve damage during surgery is rare but possible, given the proximity to important nerves in the neck.

Vocal cord paralysis affects about 1.4% of patients, according to A 25-year review of VNS complications. A small branch of the vagus nerve called the recurrent laryngeal nerve can be temporary or permanently damaged and occurs because the vagus nerve is close to nerves controlling the vocal cords.

Pain and scarring at the implant sites are normal parts of healing and are usually manageable with over-the-counter pain medication.

Device-Related Complications

Once the VNS device is implanted, other Vagus Nerve Stimulation Side Effects can emerge. Lead wire issues like fractures are rare but require surgery to fix. Pulse generator malfunction is uncommon but can be serious, with extremely rare reports of it causing vocal cord paralysis due to unexpected electrical discharge.

Battery depletion is expected, with the battery lasting 5 to 15 years depending on settings. A minor surgery is required to replace the pulse generator when the battery is low.

Device migration, where the pulse generator shifts from its original position, can cause discomfort and may require repositioning surgery.

Understanding these risks helps you know what to monitor during your VNS journey. Learn more about the Vagus Nerve Stimulator and how these devices function.

Common Side Effects During VNS Stimulation

After the VNS device is activated (typically 2-4 weeks post-surgery), you may experience effects from the electrical stimulation. Most of these side effects are mild and occur only during the brief periods when the device is actively sending pulses (e.g., for 30 seconds every 5 minutes). These are known as “on-phase” effects and fade when the stimulation cycle ends.

Understanding Common Vagus Nerve Stimulation Side Effects

The most common side effect is voice changes or hoarseness, affecting about 35.5% of patients. This occurs because the vagus nerve is near the nerves controlling the vocal cords. Your voice might sound deeper or raspier during stimulation.

Coughing is also frequent, reported by about 13.9% of patients, often described as a tickle in the throat. Throat pain or discomfort affects roughly 12.9% of people.

Some patients experience shortness of breath (dyspnea) with more intense stimulation settings. This feeling is usually mild and lasts only for the duration of the stimulation pulse.

Tingling sensations (paresthesias) can create a prickling or buzzing feeling in the neck, throat, or face. Headaches affect about 6% of patients, and neck pain near the implant site can also occur.

Encouragingly, these common side effects tend to diminish over time as your body adapts. Your healthcare team can also adjust stimulation settings to minimize discomfort while maintaining therapeutic benefits. This adaptability is a key aspect of how neurostimulation works.

Cardiorespiratory Effects of VNS

The vagus nerve helps regulate your heart and breathing, so VNS can affect these systems in subtle ways. These changes are usually mild and not a clinical concern for most patients.

Increased breathing frequency is a consistent effect, where your breathing rate may increase slightly during stimulation, while tidal volume (the amount of air per breath) may decrease. Bradycardia, a slight decrease in heart rate, occurs in most patients during stimulation, reflecting the vagus nerve’s natural function.

These cardiorespiratory changes happen during both rest and exercise. The magnitude of these measurable changes does not always correlate with the sensation of shortness of breath. If you have sleep apnea, VNS therapy might worsen the condition, which is why your medical team will carefully evaluate your breathing before recommending therapy.

Unlike many epilepsy medications, VNS therapy does not cause cognitive side effects, allowing your mind to stay sharp as your body adapts.

Serious, Rare, and Long-Term Vagus Nerve Stimulation Side Effects

While most Vagus Nerve Stimulation Side Effects are mild, it’s crucial to be aware of the more serious, albeit rarer, complications.

Significant Cardiac and Laryngeal Risks

The vagus nerve’s role in regulating the heart and vocal cords makes these areas susceptible to serious side effects:

• Bradycardia (slow heart rate): While a slight decrease in heart rate is common, it can rarely become clinically significant, requiring medical attention.
• Asystole (cardiac arrest): This is an extremely rare but life-threatening complication involving a temporary stop of heart activity. To minimize this risk, VNS is typically implanted on the left vagus nerve, which has less influence on heart function than the right.
• Left vocal cord paralysis: Permanent paralysis is a rare but serious complication. It can result from surgical injury or, in very rare cases, from a device malfunction causing continuous, inappropriate stimulation.
• Dysphagia (difficulty swallowing): Severe or persistent difficulty swallowing can occur, especially with vocal cord dysfunction.
• Risk of aspiration pneumonia: If swallowing is significantly impaired, there is an increased risk of food or liquid entering the lungs, which can lead to pneumonia.

These serious risks underscore the importance of careful patient selection and expert surgical technique. For more details, you can review this Scientific review on VNS side effects and long-term safety.

Long-Term Considerations and Other Potential Issues

Beyond acute side effects, there are long-term aspects to consider with VNS therapy:

• Sleep apnea (new onset or worsening): VNS can potentially cause or worsen sleep apnea, which is monitored during follow-up appointments.
• No reported cognitive side effects: A significant advantage of VNS is that, unlike many antiepileptic drugs, it has not been reported to cause cognitive issues. Patients may achieve seizure control without compromising cognitive function.
• Device dependency: Patients rely on the device for its therapeutic effects. If turned off or malfunctioning, these benefits will cease.
• Need for battery replacement surgery: The device’s battery depletes after 5-15 years, requiring a minor surgical procedure to replace the pulse generator.
• MRI safety precautions: Many newer VNS models are “MRI conditional,” allowing scans under specific precautions. Always inform your healthcare team and MRI technicians about your implant before any scan. X-rays and CT scans generally do not affect VNS therapy.

Understanding the full scope of options is part of our commitment to education. Learn more about More info about Neuromodulation Devices.

Implanted VNS vs. Non-Invasive tVNS: A Side Effect Comparison

When exploring Vagus Nerve Stimulation Side Effects, it’s important to distinguish between surgically implanted VNS and non-invasive transcutaneous VNS either in the neck (nVNS) or at the ear or transauricular(taVNS). Their side effect profiles differ significantly.

Surgically implanted VNS is FDAapproved for epilepsy (since 1997) and depression (since 2005). In contrast, tVNS devices available in the US are often marketed for wellness and may not have the same level of clinical evidence or regulatory oversight.

Side Effects of Surgically Implanted VNS

Implanted VNS has two phases of potential side effects: those from the surgery itself (infection, bleeding, anesthesia complications) and ongoing effects from the device.

Because the device directly stimulates the vagus nerve, it causes systemic effects. This is why patients may experience hoarseness, cough, and cardiorespiratory changes. Another reality is the need for device replacement surgery every 5-15 years to change the battery.

Side Effects of Transcutaneous VNS (tVNS)

Transcutaneous VNS delivers electrical pulses through the skin, typically on the ear or neck, avoiding the risks of surgery.

The side effects of tVNS are generally limited to the electrode application site. Research involving over 1,300 participants shows the most common issue is local skin irritation, affecting about 18.2% of users. This is typically mild and resolves after removing the device.

Other reported side effects include headaches (3.6%), nasopharyngitis (cold-like symptoms, 1.7%), dizziness, and tingling at the stimulation site. These are generally mild and temporary.

Only 2.6% of participants in research studies stopped using tVNS due to side effects. Of 30 serious adverse events reported across all studies, only 3 were possibly related to the tVNS treatment.

The choice between implanted VNS and tVNS depends on the condition’s severity and a patient’s tolerance for surgical risk. For treatment-resistant epilepsy or severe depression, implanted VNS may be worth the risks. For others, tVNS offers a safer entry point into vagus nerve therapy.

Management, Contraindications, and Unregulated Devices

Understanding how Vagus Nerve Stimulation Side Effects are managed and what situations make VNS therapy unsuitable is key. It is also important to recognize the risks of unregulated commercial devices.

How Are Vagus Nerve Stimulation Side Effects Managed?

Most common VNS side effects are manageable and often diminish over time as the body adapts.

Adjusting stimulation parameters is the primary management tool. A clinician can fine-tune the device’s current strength, pulse width, frequency, and on/off cycle timing to find a balance between efficacy and comfort. For example, adjusting the VNS pulse width can reduce side effects like hoarseness.

Gradual increase of stimulation intensity is a key strategy. The device is activated at a low setting and slowly increased over weeks or months, allowing the body to adapt and minimizing initial side effects.

Using the patient magnet provides temporary control. Passing the magnet over the implant site can stop stimulation, which is useful for activities like public speaking. For epilepsy patients, the magnet can also deliver an extra burst of stimulation to potentially stop an oncoming seizure.

Regular physician follow-ups are crucial for monitoring therapeutic response, assessing side effects, and making necessary adjustments. This ongoing partnership is part of successfully living with VNS.

Who Should Avoid implanted VNS? (Contraindications)

VNS is not suitable for everyone. The following conditions may make the therapy inappropriate:

• Patients with only one vagus nerve: Since VNS is typically implanted on the left side, damage to this nerve may preclude VNS as an option.
• Pre-existing cardiac conditions: Certain heart arrhythmias or other significant cardiac issues may increase the risk of adverse events. A thorough cardiology evaluation is essential.
• Pre-existing severe respiratory disease or sleep apnea: VNS can affect breathing and potentially worsen sleep apnea, making it risky for patients with severe or uncontrolled respiratory conditions.
• Progressive neurological diseases: VNS is generally not recommended for progressive diseases where risks may outweigh uncertain benefits.

The Dangers of Commercial and Non-Prescription VNS Devices

There are both non invasive FDA cleared vagus nerve stimulators ( such as gammaCore which has 6 different FDA clearances and and has been subjected to the rigors of FDA analysis and certain wellness devices that have not been fully evaluated by the FDA, A significant concern is the proliferation of non FDA approved commercial devices claiming to provide “VNS” for wellness purposes. These products pose considerable risks.  If the frequency and amplitude used in a non invasive vagus nerve stimulation device has not been studied, it may not be effective, or worse, could be dangerous.   

• Lack of FDA regulation for some wellness products: Many products avoid medical device regulations by marketing themselves for “wellness,” meaning they have not undergone rigorous safety and efficacy testing.  The frequency in some welleness devices, like Truvaga have undergone extensive testing, while other devices have not been studied,
• Unproven efficacy and safety for unvalidated wellness products: These devices make claims without scientific backing, and their safety profiles are largely unknown.
• Risk of incorrect nerve stimulation: The vagus nerve connects to vital organs, including the heart. Improper stimulation could trigger serious cardiac issues. Clinical devices are precisely programmed by professionals, a safety measure non-prescription devices lack.
• Potential for unknown side effects: Without medical supervision  proper testing and validation of efficacy of devies, users could experience serious, unstudied side effects.
• Importance of medical supervision: Any form of vagus nerve stimulation should only be undertaken with qualified medical guidance to ensure proper diagnosis, device selection, safe programming, and monitoring.

Frequently Asked Questions about VNS Side Effects

Here are answers to common questions about Vagus Nerve Stimulation Side Effects.

Do VNS side effects go away?

Yes, many common side effects like hoarseness, coughing, and throat discomfort tend to diminish or resolve during the first year of therapy. This occurs as your body adapts and as your healthcare team adjusts device settings to optimize comfort and effectiveness. However, some effects, particularly voice changes, may persist during active stimulation cycles. Most patients find the therapeutic benefits outweigh these mild, intermittent effects.

Can VNS cause permanent damage?

Permanent damage from VNS is rare but possible. The most significant risk is permanent vocal cord paralysis, which can result from the implantation surgery or, in extremely rare cases, from device malfunction. Reassuringly, most other Vagus Nerve Stimulation Side Effects are reversible, as they are directly tied to the electrical stimulation and stop if the device is adjusted or turned off.

Can you have an MRI with a VNS device?

Yes, in many cases. Most newer VNS models are “MRI conditional,” meaning an MRI is safe under specific, controlled conditions. These conditions may relate to the MRI scanner’s strength and which body parts can be scanned. Your VNS device may need to be temporarily turned off.

It is critical to always inform your healthcare team and MRI technicians about your implant before any MRI. They must verify your device model and follow all safety protocols to protect both you and your device. Standard X-rays and CT scans do not pose a risk to VNS devices.

Conclusion

This guide has covered the full spectrum of Vagus Nerve Stimulation Side Effects, from immediate surgical risks to long-term considerations. Most patients find VNS therapy manageable, with common side effects like hoarseness and throat discomfort typically diminishing as the body adapts.

A key advantage of VNS is what it doesn’t do. Unlike many medications for epilepsy or depression, VNS is not associated with cognitive impairment, allowing patients to maintain mental sharpness while receiving treatment.

The therapy represents a balance of risks and benefits, offering a valuable path forward for those with treatment-resistant conditions. While surgical risks are real, they are well-managed, and ongoing side effects are often mild compared to the potential life-changing benefits.

A strong partnership with your healthcare team is essential for success with VNS. Through regular follow-ups, your device can be fine-tuned to optimize therapeutic effects while minimizing side effects. This is not a “set it and forget it” treatment but an ongoing collaboration.

At Neuromodulation, we believe education empowers better healthcare decisions. Understanding the complete picture of potential side effects helps patients and providers make informed choices. Every person’s experience with VNS is unique, making open communication with your medical team crucial for navigating your individual journey.

Learn more about Vagus Nerve Stimulation (VNS) and other neuromodulation therapies.