A seizure is defined as a temporary change or disruption in the way the brain sends electrical signals1. Epilepsy is a neurological condition that is diagnosed when someone is at risk for recurrent, unprovoked seizures. Medications are the first-line treatment for seizure control, and they are highly effective for many individuals. Around 70% of people with epilepsy will achieve seizure control with one of the first two anti-seizure medications (ASMs) they try 2. However, for those whose seizures persist despite medication, other treatment options are available.
For individuals with drug-resistant epilepsy, surgery offers the best chance for seizure freedom when they are determined to be candidates. Surgical interventions aim to remove or alter the specific area of the brain where seizures originate, providing a potentially curative approach. If surgery is not an option, or if additional seizure control is needed, neuromodulation devices can be considered alongside medication to help reduce seizure activity.
The seizure control devices mentioned within this blog all utilize forms of neuromodulation to help manage seizures. Neuromodulation is the altering of nerve activity through targeted delivery of a stimulus, to specific neurological sites in the body. The three most common neuromodulation devices are the Vagus Nerve Stimulator (VNS), Responsive Neurostimulation (RNS) and Deep Brain Stimulation (DBS). These devices use electrical stimulation in an attempt to re-regulate the brain’s electrical activity and prevent or reduce seizures.
Determining eligibility for neuromodulation devices involves comprehensive testing and consideration of various factors, including seizure type, seizure focus area, age, and potential contraindications. Not all patients will be candidates for every device, and these treatments are typically used in tandem with medication rather than as standalone solutions. If you have questions or are interested in exploring neuromodulation as a treatment option, speak with your doctor to determine the best course of action for your individual needs.
Vagus Nerve Stimulator (VNS):
How it Works:
The VNS is a small device that is implanted under the skin of the chest that attaches to, and sends electrical impulses to the vagus nerve, which then transmits the signal directly to the brain. The device can be programmed to deliver stimulation at regular intervals and adapted by the patient’s neurology provider to fit their specific needs.
Effectiveness:
Studies show that approximately 50-60% of patients experience a meaningful reduction in seizure frequency with VNS, though complete seizure freedom is less common. Patients typically continue taking anti-seizure medication alongside VNS therapy. In most cases, seizure control tends to improve over time, with some individuals achieving greater reductions in seizure frequency after several years of use.
Who Qualifies for a VNS:
The VNS is available for patients aged four years and older who have generalized or focal seizures that are not fully controlled by medication.
Surgery & Recovery:
The VNS device is implanted through a relatively quick surgical procedure involving a small generator placed in the chest with a wire going to the vagus nerve in the neck.
Most individuals are able to receive this as outpatient surgery, going home the very same day and returning to their regular activities within two weeks.
As this procedure does not involve surgery directly in the brain, it is considered the least invasive among neuromodulation options.
Upkeep:
This device requires a battery replacement on average every six years depending on the device and its stimulation settings. Battery replacement requires a minor surgery.
Potential Side Effects:
The most common side effects of VNS include voice alteration (such as hoarseness while talking), throat pain, coughing, shortness of breath, tingling or muscle pain3. As is true of all surgical procedures, there is a risk of surgical site infection if the incision site is not properly cleaned or cared for. This risk reduces within a few weeks, once the surgical wound fully heals.
Responsive Neurostimulation (RNS):
How it Works:
The RNS System provides closed loop neurostimulation when abnormal electrical activity is detected in the brain. The stimulator is implanted on the skull, with electrode leads placed directly at the site of seizures within the brain. The RNS continually senses the electrical activity and is specifically programmed to detect and respond to specific patterns that are seen during seizures. Additionally, the device captures electrocorticography (ECoG) data, which provides valuable insight into brain activity over time. This allows healthcare providers to review the recorded data and make individualized adjustments to the device’s detection and stimulation settings, optimizing treatment based on the patient’s unique seizure patterns and ECoGs4.
Effectiveness:
Initial studies for the RNS show a 75% reduction in seizures over time for patients with the device5, with some patients achieving long-term seizure freedom. Studies have shown that the RNS system becomes more effective over time, with patients seeing a decrease in seizure activity over time.
Who Qualifies for a RNS:
People with drug-resistant epilepsy, over the age of 18 who have undergone comprehensive diagnostic testing but are not eligible for certain brain surgeries, may be eligible for the RNS system. RNS implantation typically requires intracranial monitoring to establish the seizure focus and determine electrode placement. This monitoring process is often conducted weeks prior to implantation to ensure accurate placement and optimal effectiveness of the device.
Surgery & Recovery:
The RNS system requires surgery to place the device under the scalp with leads connecting within the brain. The surgery itself lasts about 1-3 hours during which time the patient will be placed under anesthesia. Many individuals can go home the next day after being cleared by their medical team, some may need to stay a few extra days inpatient for recovery. Many patients can return to regular activity within a few weeks and may even be able to return to work in 2-4 weeks.
Upkeep:
The RNS system will require a battery change every three to twelve years, depending on the model implanted as well as settings within the device. Newer models typically last an average of 9 years. The battery replacement requires minor surgery. Additionally, ongoing patient and family engagement is crucial for the successful use of the RNS system. Patients or caregivers must regularly transfer and upload data from the device to ensure healthcare providers can monitor seizure activity and make necessary adjustments. This routine data sharing helps optimize treatment
Potential Side Effects:
There are typically no long-term side effects relating to the implantation of the device. However, though uncommon, side effects can happen as a result of the surgery including bleeding, brain damage, infection and pain. It is possible that the device may not improve seizure activity in some individuals.
Deep Brain Stimulation (DBS):
How it Works:
DBS is a process in which electrical wires are strategically placed in the brain and attached to a pulse generator which is surgically implanted underneath the skin near a person’s collarbone6. The electrical pulses help to stimulate neurons within the brain which could be causing seizures as well as some other movement disorders. Similar to VNS, it is programmed to deliver stimulation at regular intervals.
Who Qualifies for a DBS:
Adults 18 years or older with medication resistant focal epilepsy. DBS may be an option for individuals who are not eligible for other types of brain surgery.
Surgery & Recovery:
The implantation of DBS requires multiple surgeries happening at different times. First, the electrodes will get implanted in the area of focus within the brain. Then, the pulse generator will be implanted under the skin just below the collarbone that will attach to an extension wire connected to the electrodes. Similar to the RNS system surgery, patients may stay in the hospital for a few days for recovery and then will go back to their regular lifestyles within a few weeks.
Upkeep:
The pulse generator battery will need to be replaced every three to nine years, depending on the installation model. This replacement requires minor surgery.
Potential Side Effects:
As with all surgical procedures, there is a risk of infection, bleeding, and other surgical complications. Side effects from the device itself could include balance problems, confusion, trouble focusing, memory problems, numbness, or other changes in brain function.
Conclusion:
VNS, RNS, and DBS are all neuromodulation treatment options for drug-resistant epilepsy, each offering unique mechanisms of action. VNS stimulates the vagus nerve to modulate brain activity, RNS provides responsive electrical stimulation directly at the seizure focus, and DBS delivers continuous stimulation to deep brain structures. While VNS is the least invasive and does not require direct brain surgery, RNS and DBS involve intracranial implantation to target specific brain areas. RNS stands out by capturing ECoG data, allowing providers to adjust settings based on a patient’s individual seizure patterns. Despite their differences, all three devices are typically used alongside medication rather than as standalone treatments. Choosing the best option depends on a variety of factors, including seizure type, location, and overall health considerations, making close collaboration with healthcare providers essential in the decision-making process.
The information, including text, graphics, images and other material on this website and provided by the Epilepsy Foundation of Northeastern New York, is for informational purposes only. No material on this site is intended to be a substitute for professional medical advice, diagnosis or treatment.
If you are interested in learning more about seizure recognition and first aid, please reach out to our team by calling (518) 456-7501 or visiting our website for additional resources.
Citations
1 Epilepsy and seizures | National Institute of Neurological Disorders and stroke. (n.d.). https://www.ninds.nih.gov/health-information/disorders/epilepsy-and-seizures
2 Hakami, T. (2021, September 26). Efficacy and tolerability of Antiseizure Drugs. Therapeutic advances in neurological disorders. https://pmc.ncbi.nlm.nih.gov/articles/PMC8481725/
3 Vagus nerve stimulation. AANS. (2024, April 10). https://www.aans.org/patients/conditions-treatments/vagus-nerve-stimulation/
4, 5 Nair, D. R., Laxer, K. D., Weber, P. B., Murro, A. M., Park, Y. D., Barkley, G. L., Smith, B. J., Gwinn, R. P., Doherty, M. J., Noe, K. H., Zimmerman, R. S., Bergey, G. K., Anderson, W. S., Heck, C., Liu, C. Y., Lee, R. W., Sadler, T., Duckrow, R. B., Hirsch, L. J., … RNS System LTT Study. (2020, September 1). Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy. Neurology. https://pmc.ncbi.nlm.nih.gov/articles/PMC7538230/
6 Deep Brain Stimulation (DBS): What it is, Purpose & procedure. Cleveland Clinic. (2024, May 1). https://my.clevelandclinic.org/health/treatments/21088-deep-brain-stimulation
