Implant devices are used to treat seizures in people with refractory or drug-resistant epilepsy. This means that their seizures are not controlled after trying two or more appropriate anti-seizure medications. Implants may be recommended for people for whom brain surgery to remove the area where the seizures start is not an option, or when surgery did not work.
Implant devices can help to reduce the frequency and severity of seizures, but are not expected to stop seizures completely. Some people may be able to decrease the dosage of their medication, which may help reduce side effects.
VNS (Vagus Nerve Stimulation)
VNS involves having a small device implanted under the skin of the left chest and connected through a wire to the vagus nerve in the neck. The device is programmed to deliver mild pulses of electrical energy at regular intervals to areas of the brain that are associated with seizures. This can help to prevent or lessen seizures.
The person doesn’t need to do anything to make the device work, and is usually unaware of when the stimulation is happening. If the person is aware that a seizure is beginning, they can swipe a magnet over the device to prompt it to send an extra burst of electrical stimulation to the brain. This may help to stop the seizure.
Newer VNS models can pick up a fast increase in heart rate that is experienced by many people prior to a seizure. This triggers an extra burst of stimulation that may stop the seizure. These models may be especially helpful for people who aren’t aware of when their seizures happen (for example, at night when no one witnesses them).
VNS Therapy® is approved by the U.S. Food and Drug Administration (FDA) as an add-on therapy for adults and children 4 years and older. This means it is used in combination with anti-seizure medications.
VNS is used primarily for focal (partial) seizures, but people with some types of generalized seizures, including Lennox Gastaut Syndrome, have also benefited. This therapy does not cure epilepsy, but is designed to help reduce the number and severity of seizures. Reduction in seizures typically improves over time, from an average reduction of 28% in the first three months to as much as a 75% decline in seizures after 10 years of use.
In addition to seizure reduction, people with VNS have reported other benefits, including:
- Decreased severity of seizures
- Shorter recovery time
- Improved quality of life
- Less worry about seizures
- Improved alertness
The most common side effects of the VNS are:
- Shortness of breath
- Sore throat
As with all surgeries, there is a risk of infection from the procedure to implant the device.
RNS (Responsive Neurostimulation)
The RNS® System consists of a small pacemaker-like device (neurostimulator) connected to electrodes by tiny wires (leads). The device is placed in the skull under the scalp, and the electrodes are connected to up to two areas of the brain where the seizures come from. These electrodes continuously record electrical activity in the brain. When a seizure or seizure-like activity is detected, the device responds by delivering a small amount of electrical current to the brain to stop or shorten the seizure, or possibly even prevent the seizure altogether. The individual does not feel the stimulation happening.
Because placement of the electrodes is individualized to each person, doctors will perform extensive diagnostic testing prior to placement of the device in order to determine the specific locations where the seizures originate. Once the device is in place, it is programmed to deliver the appropriate amount of stimulation. The individual uses a remote monitor to wirelessly download information to a secure database. This allows the doctor to review the data and make adjustments to the programming of the device as needed to achieve the best results.
RNS Therapy® is approved by the FDA as an add-on therapy for adults 18 and older. This means it is used in combination with anti-seizure medications.
RNS is designed for use in people with focal (partial) seizures. This therapy does not cure epilepsy, but has been shown to reduce the number of seizures in most people. Studies have shown these results to improve over time, from an average reduction in seizures of 44% after one year, to 53% at two years, to 66% percent at three to six years. A long-term study showed a median seizure reduction of 75% after nine years. In addition, almost 1/3 of the individuals studied had a seizure-free period of six months or more.
In addition to seizure reduction, people with RNS have reported other benefits, including:
- Improved physical health
- Better cognitive functioning (thinking, remembering, concentrating, etc.)
- Improved emotional health or mood
- Less worry about seizures
- Higher overall quality of life
The primary side effects associated with RNS are the same as for any surgical procedure, such as risk of infection or bleeding.
DBS (Deep Brain Stimulation)
In DBS, a device called a neurostimulator is implanted under the skin in the upper chest and programmed to send tiny electrical impulses directly to the brain. These impulses travel through wires (leads) to electrodes, which are implanted in a part of the brain that is involved in the spread of seizures. These electrical impulses help to stop seizures from beginning or spreading to different areas of the brain. The person typically does not feel these impulses happening.
Because every individual is different, personalized therapy settings are programmed by the doctor using wireless communication with the implanted device. These settings may be adjusted over time to best reduce seizures and side effects. The individual may be given a small device that allows them to turn the system on and off, check the battery, and change the stimulation within the options programmed by the doctor. The positive effects of DBS may not occur right away, and it can take up to two years to get the full benefit.
Extensive testing is required prior to implantation to determine if the individual is a good candidate for DBS, and to perform detailed mapping of the brain to guide the surgeon in implanting the electrodes.
DBS is approved by the FDA as an add-on therapy for adults age 18 and up who have focal (partial) seizures. The individual will continue to take anti-seizure medications. Candidates for DBS typically have tried three or more anti-seizure medications without achieving seizure control, and have averaged more than six seizures per month for the past three months, with no more than 30 days between seizures.
DBS does not cure epilepsy, but aims to reduce the frequency and severity of seizures. A clinical study showed 43% of participants achieved seizure reduction of more than 50% in the first year. That rate improved over time, with 75% of participants achieving greater than 50% seizure reduction by year seven. In addition, nearly 1 in 6 experienced at least six months of freedom from seizures in the seven years after implant.
In addition to seizure reduction, clinical studies showed other benefits of DBS, including better quality of life and reduction in seizure-related injuries.
Possible side effects of DBS include:
- Tingling at the implant site, which may be resolved with adjustments to the device programming
- New or worsening neurological or psychiatric symptoms, including depression, suicidal thoughts and suicide
- Changes in seizures (new seizure type or worsening seizures such as increased seizure frequency, duration, and/or severity)
- Risks of the surgery itself, including bleeding in the brain, infections at the site of the implant, depression and memory problems