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With an implanted VNS Therapy System, hoarseness or another voice change during stimulation is the most commonly reported stimulation-related side effect in FDA patient labeling. Cough, throat symptoms, tingling, shortness of breath, indigestion, and nausea are also reported. Don’t stop prescribed VNS just because of a routine, brief effect: contact your VNS team promptly about persistent hoarseness, breathing or swallowing problems, painful or irregular stimulation, or a sudden loss of stimulation. If you mean an external, non-invasive stimulator, its risks and instructions are different.
First, identify which kind of VNS you use
This article focuses on implanted VNS, especially the FDA-labeled VNS Therapy System. “Vagus nerve stimulation” can also mean an external device used on the skin. Its labeling and side effects are not interchangeable with those of an implant. For example, FDA labeling for the prescription gammaCore Sapphire CV lists application-site discomfort or redness, local pain, facial or neck muscle twitching, headache, dizziness, and tingling. Those effects do not establish the rates or risks of implanted VNS. See the gammaCore FDA labeling.
Which side effects are common with implanted VNS?
Voice changes and throat effects
Hoarseness or voice alteration is identified as the most common stimulation-related effect in the FDA patient manual for the VNS Therapy System. It generally occurs during the device’s ON period. Its intensity can range from severe to barely noticeable, depending in part on stimulation settings.
The manual also reports cough, pharyngitis (throat inflammation), and laryngismus (a spasm involving the voice box). In its historical observed adverse-event table, based on 314 patients in a randomized study plus long-term follow-up, voice alteration was reported in 50%, increased coughing in 41%, pharyngitis in 27%, and laryngismus in 3.2%. These are results from that study population, not universal rates for every current model, indication, or patient.
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Other reported effects
The same historical table lists paresthesia (tingling) in 28%, shortness of breath in 18%, nausea in 19%, and dyspepsia (indigestion) in 12%. The figures describe that particular study population; individual effects and severity vary.
A separate FDA patient manual for the D-02 depression study reports stimulation-related voice alteration in 59% at 3 months, 54% at 12 months, and 52% at 24 months; increased cough in 24%, 7%, and 4%; and shortness of breath in 14%, 16%, and 14%, respectively. These are time-specific, study-specific results and should not be treated as estimates for all VNS users. See the FDA D-02 study patient manual.
When should you contact your VNS care team?
Use the symptom’s timing and impact to describe what is happening: whether it occurs only while stimulation is on, whether it persists between cycles, how severe it is, and whether it affects breathing, swallowing, sleep, or daily activities. Contact your VNS team promptly about the following concerns.
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Hoarseness that continues between stimulation periods
A brief voice change that occurs during stimulation is different from hoarseness that persists when stimulation is off. FDA physician labeling says persistent hoarseness not associated with stimulation may indicate nerve irritation and should be investigated immediately. Report it to your clinician rather than assuming it is a routine stimulation effect. See the FDA physician labeling.
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Breathing difficulty or changes during sleep
Shortness of breath can occur during active stimulation. FDA physician labeling also warns that VNS may increase obstructive sleep apnea events or cause new-onset sleep apnea, and that patients with pulmonary disease may be at increased risk. Report new or worsening breathing symptoms, including sleep-related changes, promptly.
Swallowing difficulty, choking, or aspiration concerns
Stimulation can cause difficulty swallowing (dysphagia). Increased swallowing difficulty may raise the risk of aspiration, when food or liquid enters the airway. The physician manual notes that pausing stimulation with the magnet while eating may mitigate this risk. Follow the instructions for your specific device and the plan given by your care team; do not assume the magnet is appropriate for every situation.
Painful, irregular, or unexpected stimulation
FDA physician labeling warns that a device malfunction can cause painful stimulation or direct-current stimulation, with potential nerve damage. If you suspect an implanted-device malfunction, the manual instructs patients to use the magnet to stop stimulation and contact their physician immediately for evaluation. Prompt surgical intervention may be required. This is a specific instruction for suspected malfunction, not general advice to stop prescribed therapy for ordinary side effects.
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Some patients may notice when stimulation stops. An FDA Class 2 recall notice concerns specified SenTiva and SenTiva Duo generators that may stop delivering stimulation. The recall was initiated December 12, 2024, and posted January 31, 2025; it applies to specified serial numbers below 500,000, not automatically to every generator of those models. If you have one, check the FDA recall notice and contact your VNS team to confirm whether your model and serial number are affected. Report changed clinical symptoms or no longer perceiving stimulation; the notice advises clinicians to run diagnostics.
The labeling reviewed here does not define one emergency-care rule for every symptom. For severe or rapidly worsening symptoms, follow local emergency guidance and the plan provided by your clinician.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Should you stop VNS because of a side effect?
Do not treat every familiar, brief stimulation effect as a reason to stop prescribed therapy. Instead, tell your VNS team if an effect is bothersome or interferes with daily life; stimulation settings may be adjusted by the clinician. Persistent symptoms, swallowing or breathing problems, painful or irregular stimulation, and a sudden loss of stimulation call for prompt contact. The magnet instruction is specifically for suspected device malfunction, as described above. Make device-setting or treatment decisions with your care team.
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