Who are candidates for VNS?
VNS candidates are people with refractory or “drug-resistant” epilepsy (DRE) of any age and seizure type. “Drug-resistant” means seizures are not controlled after trying at least two (2) appropriately chosen and tolerated anti-epilepsy drugs (AEDs), alone or in combination, to control seizures when used for an adequate period of time [ILAE/Ontario Guidelines definition]. Studies show that one third of people living with epilepsy are Drug-resistant.
VNS Therapy is a viable option for individuals with DRE after it has been determined by the Epilepsy Team at a Comprehensive Epilepsy Center (CEC) that they are not suitable for epilepsy surgery. VNS Therapy is an adjunct treatment, which means it is used in addition to seizure medication and/or other therapies.
What is VNS?
VNS Therapy® (also called Vagus Nerve Stimulation) has been Health Canada approved since 1997 for people of all ages with refractory epilepsy. It is an adjunct treatment (used with medications), and the cost is fully covered by provincial health care systems; no cost to the patient.
VNS Therapy is an implanted system that sends mild electrical stimulation to the left vagus nerve that runs along the outer aspect of the neck and carries signals to the brain, leading to changes that make the brain more calm and less likely to have seizures. A small pacemaker-like generator device implanted just under the skin in the left chest area delivers electrical impulses to the vagus nerve (via an electrode placed in the neck) at regular intervals around the clock, 24 hours a day, every day.
The two components of the system (generator and electrode lead) are surgically implanted in a procedure done under general anesthesia, typically taking 60-90mins. It is not brain surgery; the two small incisions needed are at the mid-neck and just below the collarbone. In most cases the person can go home the same day or the next day.
Either at time of implantation or after a short healing period of up to two weeks, the pulse generator is turned on by the doctor or nurse to begin sending a particular “dosage” of stimulation to the vagus nerve, typically 30 seconds of stimulation, at five-minute intervals, with a strength of 0.25 milliamperes (mA) of electrical current. This is a very low dose, and is not expected to provide much benefit, if any. The device can then be set to gradually increase the output over time, so that within about two months the device is delivering a more suitable amount of therapy. It will be necessary to visit the doctor or clinic periodically to ensure the best settings for seizure control and tolerance have been selected for the person. Once the ideal “recipe” for stimulation, combining device output and on/off sequencing, has been determined, follow-up with the neurologist returns to usual frequency.
What benefits can I expect?
VNS Therapy is not a cure for epilepsy. Although some people become seizure free (approximately 1 in 10), it is designed to prevent seizures from occurring and help control seizures by lessening their number, their severity, and their duration when they do occur. VNS has also been shown to decrease recovery time from a seizure as well as provide a meaningful improvement in quality of life.
The majority of people receiving VNS will gain some benefit, but there are some that will not. A study of 436 people found that by 5 years after implantation, almost two-thirds of all patients experienced a seizure reduction of at least 50%, and nearly one-in-four had a seizure reduction of 90% or better. Some people respond quickly, while others require more time to allow the increases in dosage of stimulation to reach therapeutic levels. It may take some months before any improvement is experienced. Other studies have shown that the benefits of VNS Therapy continue to increase over time, even out past five years. More recent data from 2018 showed that using the newer autostimulation mode in addition to usual stimulation resulted in 59% of the people treated having at least a 50% seizure reduction in 13 months, which is earlier than previous reports of “traditional” VNS Therapy.
A review of 65 people who had VNS for 10 years or more, showed improvements in seizure control over time. Seizures decreased by 36% after 6 months, 52% after 1 year, 61% after 4 years, and 76% by year 8. A 2017 study showed that 8 out of 10 people receiving VNS reported an improved quality of life.
Are there side effects?
The implantation of a VNS device is done via a short surgical procedure. There is a small risk of infection in about 1-3% of cases in the first few weeks following the procedure. The main side effects reported with VNS Therapy occur only when the device is providing stimulation (“ON”) to the vagus nerve. The most common are voice hoarseness, cough, a tingling sensation in the throat, and shortness of breath. Most people report a reduction in side effects over time as the body gets accustomed to the therapy. Also, if side effects do occur, adjustments to the device settings may reduce or eliminate them.
VNS Therapy has been used for over 20 years in Canada and has been deemed safe for long-term use. The safety and efficacy of VNS Therapy has not been established for use during pregnancy; however, pregnancies have gone to term in women receiving VNS Therapy. There are no known drug interactions with VNS Therapy, and other treatments can be used in conjunction with VNS Therapy. Medication-like side effects, such as sleepiness, or low energy do not occur with VNS Therapy.
An epilepsy specialist can help you learn more about VNS Therapy, and other treatment options which might be right for you.