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How Neurostimulation Devices for Epilepsy Differ: RNS vs. VNS and DBS
June 29, 2022Reading Time: 5 Minutes
- Neurostimulators treat focal seizures with electrical pulses when medications aren’t enough and removing or destroying brain tissue may cause harm.
- You and your doctors can choose from among three approved options, with key differences in seizure targeting and data recording.
- The RNS System is the only neurostimulator that provides therapy when it’s needed, lets doctors view your data online, and comes without long-lasting stimulation side effects.
Treating focal seizures with electrical stimulation
When epilepsy doesn’t respond to medication, doctors may consider surgery to remove the brain tissue where seizures start. They may also consider laser ablation to heat and destroy the tissue. However, doctors often decide neither approach is possible — seizures may not have clear origins or involve too much of the brain. Removal or heating might damage sensitive areas such as speaking and motor control.
When surgery or ablation aren’t possible — or when they don’t provide freedom from seizures — doctors can turn to special devices. These battery-powered devices are called neurostimulators and are implanted in the body. The Food and Drug Administration (FDA) has approved three of them to treat drug-resistant epilepsy.
Each device treats focal onset seizures without removing or destroying brain tissue. Each stimulates the brain with adjustable electrical current, directly or indirectly. And each provides therapy that often becomes more effective over time.
Only one device, though, responds to sudden changes in brain activity, while avoiding stimulation side effects and providing your doctor with data through an online portal.
Placement: RNS vs. VNS vs. DBS
While the three available devices all send electrical pulses, doctors place each neurostimulator and its wires in different locations:
- Responsive neurostimulation (RNS): Doctors place the RNS System inside the skull, away from the brain — a position where no one can see it. They connect the device to wires, which they run directly to the brain tissue identified as the source of seizures. The RNS device is the smallest option and the only neurostimulator that directly targets seizures at their source. It also has a long battery life — nearly 11 years, on average.
- Vagus nerve stimulation (VNS): Doctors implant the device under the skin on the left side of the chest. They connect it to a wire, which they wrap around a vagus nerve in the neck. (In some patients, bumps from the device and wires may be visible under bare skin.) Electrical stimulation travels from the nerve to the brain.
- Deep brain stimulation (DBS): Doctors put the device under the skin in the chest or belly. (Again, doing so can leave a visible bump.) They run a wire from the device through the neck, under the scalp and into the brain. They stop in an area of the brain called the thalamus. This region can influence other parts of the brain.
On average, RNS and DBS both report high reduction in seizures over time — higher than VNS1. Important distinctions exist between RNS and DBS, though.
Key Difference 1: RNS is the only device to detect seizure activity and respond immediately
Among the neurostimulators, DBS provides electrical pulses at set intervals, regardless of what happens in your brain. At appointments, your doctor can adjust the pattern, but between visits it never changes.
VNS mostly takes a similar approach, with a few features layered on. You can temporarily add extra stimulation by placing a special, included magnet to your chest. And newer models send additional pulses when they sense fast heartbeats, because a rising heart rate can sometimes indicate a seizure. The sensation is not always welcome, users say.
“It was kind of an irritant, actually,” says Adison from California. “It was like a cellphone constantly vibrating, only in your throat instead of in your pocket.”
The RNS System is different. With the device, doctors still fine-tune settings during appointments, based on response to treatment and insight from the collected data. But stimulation only happens when it’s needed, with no personal intervention required. The device senses unique seizure patterns in your brain, then sends stimulation pulses in milliseconds to control the seizure. This approach responds to a more direct measure of seizures, the patterns in your brain, rather than responding to heart rate, which may or may not indicate a seizure.
You don’t feel RNS stimulation stabilizing your brain waves, but it’s there, day and night. It’s real-time, personalized relief.
Key Difference 2: RNS makes it easy for your doctor to see seizure activity
Seizure and therapy data can be the keys doctors need to provide the most effective, personalized treatment. But neurostimulators vary in their approach. VNS simply records any extra stimulation delivered. DBS captures brain signals called local field potentials, or LFPs.
Only RNS uses electroencephalography (EEG) to measure the brain’s electrical activity — the same monitoring used at medical centers to identify seizures. It also notes when an electrical event is detected and if stimulation is delivered. It monitors constantly, then responds to seizures and records the activity. This data provides your doctors with a window into the brain and a wealth of valuable information.
Unlike with DBS, you don’t need to go to your doctor’s office to provide the data. You hold an electronic wand over the device to transfer the recordings to another, dedicated device and then upload to a secure online platform. It takes just a few minutes, and your doctor can check the data at any time. (They may see that you need to come in sooner for setting adjustments, for example.) An optional feature involves a special, round magnet that is included. You swipe it over your RNS device when you sense a seizure coming on, basically capturing your EEG and timestamping the data.
The data from the RNS System has led to valuable insights, particularly when combined with personal seizure diaries. Examples include:
- Realizing orange juice was a particular seizure trigger, for Heather of North Carolina
- Identifying the worst seizures and making sure those received special attention, for Kathleen from California
- Proving to the state that her seizures only took place while asleep, allowing Carolyn to reclaim her driver’s license
- Determining the ideal time to take seizure medications, for Carlo
- Finding out that additional surgery could still reduce seizures, for Erick from South Carolina
For Connie, it was simply the confirmation — at long last — of what was happening in her brain.
“I think my seizures are a particular kind that was hard to see or describe,” she says. Without concrete evidence to share with doctors and loved ones, she felt frustrated and alone for years.
“Finally, the RNS System, like nothing else, let people see and understand what was happening in my brain,” Connie says.
Key Difference 3: RNS comes with the least side effects
With DBS and VNS therapies, which deliver hours of stimulation per day, patients can experience ongoing side effects. People who have DBS sometimes report depression and memory problems. There can also be a feeling of anxiety and confusion.2
VNS can cause shortness of breath, sore throat and coughing, though these effects may decrease over time. The most common side effect is hoarseness, a potential impact that can give people pause.
“I talk all day at my job, so I wanted something that wouldn’t potentially tickle my throat or mess with my ability to talk,” Richard says. “I was afraid VNS would have made it harder, not easier, to do my job.”
Unlike other neurostimulators, the RNS System is well tolerated and doesn’t cause any chronic stimulation side effects2. It provides effective treatment without compromises. For Richard, that was a game-changer.
During an appointment after his RNS System placement, doctors looked at his data and noticed a point when stimulation kicked on. They asked him what he was likely doing at the time. He recalled he had been at work, and hadn’t noticed either seizure symptoms or the therapeutic response.
That realization led to an outpouring of relief when he returned to the parking lot. “I sat in my car for a little bit and cried,” Richard says. “I realized how much this decision to get the RNS System was going to change my life for the better.”
1. LivaNova VNS Therapy System Epilepsy Physician’s Manual, November 2018. Medtronic Website, 2018. Nair D, et al., Presented at AES, 2018
2. Sprengers et al., Cochrane Database of Systematic Reviews, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6483316/
*Every person’s seizures are different and individual results will vary