Vagus Nerve Stimulator (VNS)

Vagus Nerve Stimulator

VNS (Vagus Nerve Stimulator) - Cyberonics

The VNS is an implant device that consists of a generator and wires that terminate in leads which are coiled around the Vagus nerve. The generator sends electrical impulses to the nerve according to programmed parameters.


According to Cyberonics (circa 2011 - link no longer available):
The long-term impact of VNS Therapy was assessed in an open-label, long-term study of 454 epilepsy patients using data from all 5 VNS Therapy controlled, clinical trials. The study compared the percentage of patients with seizure reductions of >= 50% over a 3-year period. The percentage of patients with >= 50% seizure reduction was 36.8 at 1 year, 43.2 at 2 years, and 42.7 at 3 years.

Potential Adverse Events

According to the Physician's Manual:
Adverse events reported during clinical studies as statistically significant are listed below in alphabetical order:
  • Ataxia (muscle movements or twitching, generally associated with stimulation)
  • Dyspepsia (indigestion)
  • Dyspnea (difficulty breathing, shortness of breath)
  • Hypesthesia (impaired sense of touch)
  • Increased coughing
  • Infection
  • Insomnia (inability to sleep)
  • Laryngismus (throat, larynx spasms)
  • Nausea
  • Pain
  • Paresthesia (prickling of the skin)
  • Pharyngitis (inflammation of the pharynx, throat)
  • Voice alteration (hoarseness)
  • Vomiting, Aspiration (fluid in the lungs)
Other potential adverse events possibly associated with surgery or stimulation include but are not limited to the following:
  • Blood clotting
  • Choking sensation
  • Damage to nerves or vasculature in the surgical area, including the carotid artery and jugular vein
  • Device (Generator and/or Lead) migration or extrusion
  • Dizziness
  • Dysphagia (difficulty swallowing)
  • Duodenal ulcer, gastric ulcer
  • Ear pain
  • Facial flushing
  • Facial paralysis, paresis
  • Foreign body reaction to implants, including possible tumor formation
  • Formation of fibrous tissue, pockets of fluid
  • Heart rate and rhythm changes
  • Hiccuping
  • Incision site pain
  • Irritability
  • Laryngeal irritation (sore, painful throat)
  • Left hemidiaphragm paralysis
  • Left recurrent laryngeal nerve injury
  • Left vocal cord paralysis
  • Low-grade fever
  • Muscle pain
  • Neck pain
  • Nerve injury
  • Painful or irregular stimulation
  • Skin, tissue reaction
  • Stomach discomfort
  • Tinnitus (ringing in the ears)
  • Tooth pain
  • Unusual scarring at the incision site
  • Urinary retention
  • Vagus nerve paralysis
  • Weight change
  • Worsening of asthma and bronchitis
  • Worsening of cardiac abnormalities, including heart rate and rhythm
According to The Houston Press (Exposed Nerve):

The FDA in 1997 approved it for people more than 12 years old who suffered from treatment-resistant epilepsy. These were the unfortunate patients who had exhausted every pill, diet and surgical alternative. Although the FDA does not approve it in younger patients, off-label use -- implanting the device in kids under 12 -- is legal and common. However, Cyberonics' policy lists any adverse event in off-label use as "user error." Meaning that, technically, if Sam's device were to spontaneously combust, it would be the Goldsmiths' fault.


Up until February 2004, Cyberonics had its own forum. But the company shut it down, explaining that "Increasingly…the message board has been an instrument for abuse by certain individuals."

According to former forum members, the shutdown came on the heels of a patient posting a link to the FDA's database of product problems. The database lists 500 adverse events for Cyberonics between May and December 2004 and 1,414 for 2002. Data for 2003 is not available online. Events range from increased seizures to death, which is often described as "sudden unexplained death in epilepsy." In many cases, Cyberonics reported that surgeons refused to provide in-depth information so the company could find the cause of the problem. In one case of an inverted device, a neurologist "asked that he not be contacted regarding the event, as he has a limited staff and is subsequently not able to respond to mfr's request for additional info."

Cyberonics received a similar cold shoulder regarding a patient who died five days after implantation. In the case of one patient who developed a wheezing problem, the company could not investigate because whoever reported the problem forgot the patient's name. Some of the cases in which Cyberonics could figure out what went wrong are troubling as well, including the instance of a surgeon who implanted the device when it was already on. The device is not supposed to be activated until two weeks after surgery.

There are a few minor averse events that are common and expected for just about every VNS patient. The more severe potential adverse events appear to be less common. There are first person accounts of additional potential adverse events on the VNS Message Board. I scored the VNS Therapy as a 4 for both the common nuisance and less common very severe potential adverse events.


This procedure is cost prohibitive without insurance. It scores an 8 for a general approximation of out of pocket expenses (for what insurance does not cover).


The VNS works on a mostly passive basis once settings have been ramped up to the desired therapeutic level. It does require surgeries to replace batteries every so many years (depending upon model and settings), and patients can be active with a magnet to activate the device, but I scored it as a continuous system with passive participation because that is how it operates most of the time.


It's a real mixed bag as to when (or if) the VNS will offer assistance with seizure control. Studies indicate that the best results are obtained after at least 1-2 years.

Special Notes

The VNS system can exacerbate sleep apnea. Recent studies show that a third or more epilepsy patents also have sleep apnea.

Additionally, having the VNS implanted may make it difficult to get an MRI.

This page last modified September 9, 2019.

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