For many people with epilepsy, medications can help control or reduce their seizures and treat their epilepsy. However, approximately 30% of people with epilepsy do not respond to medication and must explore alternative therapies to control their seizures. Neurostimulation devices offer another option for reducing seizure frequency in people with drug-resistant (refractory) epilepsy.
There are only three devices approved by the FDA to reduce the frequency of seizures: Vagus Nerve Stimulation (VNS), Responsive Neurostimulation (RNS), and Deep Brain Stimulation (DBS). To reduce seizure frequency, these devices use neurostimulation, or the process by which energy, usually electrical stimulation, is applied to the central nervous system to modulate (change) brain activity.
The FDA granted each epilepsy device an approval specific to how they studied the device’s use in people with epilepsy during clinical trials. These devices have been approved by the FDA for usage when the person with epilepsy: 1) has an identified focal (partial) seizure onset, 2) is drug-resistant (antiseizure medications do not work), and 3) the person is not a good candidate for the routine surgeries used to treat epilepsy.
The VNS is like a pacemaker for the brain – it sends a mild electrical pulse to the brain through the Vagus nerve at regular intervals all day, every day to prevent a seizure. The VNS stimulator (electric pulse generator) is placed under your skin on the top left section of your chest and uses wire coils to connect to your left Vagus nerve, located in your neck. It can also be used to stop or reduce the severity or length of a seizure by delivering an additional “dose” of therapy on demand by using a magnet to manually activate the device.
VNS is approved for use as adjunctive therapy (used with antiseizure medications) in people with epilepsy who are 4 years of age or older and have focal seizures (formerly called complex partial seizures) that are refractory to antiseizure medications. Changes or adjustments to the treatment regimen may be necessary.
VNS is not brain surgery; however, there is a risk of infection during and after the surgical operation. Additionally, you may experience side effects such as hoarseness, cough, voice alteration, throat pain, exacerbation of obstructive sleep apnea (temporarily stopped breathing), and cardiac arrhythmias (irregular heartbeat).
The RNS System® is a neuromodulation device that uses electrical stimulation to prevent and treat seizures. This device is also like a pacemaker for the brain. The RNS System is implanted near the seizure focus and is flush with the skull. The RNS stimulator is placed within the skull and connects to electrodes that are placed inside your brain at the seizure focus.
However, rather than delivering stimulation continuously or on a set schedule, it monitors brainwaves for a person’s unique seizure pattern. If it detects abnormal or unusual activity at the seizure focus (where the seizure starts), it delivers a brief pulse of electrical stimulation to prevent or stop a seizure.
RNS is approved for use as adjunctive therapy (used with antiseizure medications) in people with epilepsy who are (1) 18 years of age or older, (2) have focal-onset seizures with no more than two identified foci (a place on the brain where the seizure starts), and (3) currently have frequent and disabling focal aware, focal unaware, and focal to bilateral seizures (formerly called motor partial, complex partial, and/or secondarily generalized seizures) that have not responded to two or more antiseizure medications. Changes or adjustments to the treatment regimen may be necessary.
There is a risk of infection during and after the surgical operation. Because of its placement, there is also a risk of bleeding in the head. Additionally, you may experience side effects such as infection, post-device implantation intracranial hemorrhage, and transient memory impairment.
DBS is a neuromodulation device that sends electrical pulses through wires to the specific areas of the brain involved with seizures. The DBS stimulator is placed in the left pectoral muscle of your chest. The connected DBS electrodes are typically placed inside your thalamus, which is a structure near the center of your brain. The electrical pulses block signals from the nerve cells that trigger a seizure. DBS is another device that acts like a pacemaker for the brain, and it can be programmed to deliver constant or intermittent stimulation.
DBS is approved for use as adjunctive therapy (used with antiseizure medications) in people with epilepsy who are 18 years of age or older and have focal-onset seizures (formerly called partial seizures) with or without focal to bilateral seizures (formerly called secondary generalization) that have not responded to three or more antiseizure medications. Changes or adjustments to the treatment regimen may be necessary.
There is a risk of infection during and after the surgical operation. Because of its placement, there is also a risk of bleeding in the head. Additionally, you may experience side effects such as paresthesia (abnormal body sensations), subjective memory impairment, and depressed mood; implant site pain and infection; and incidentally found intracranial hemorrhage (bleeding in the head).
The future of neuromodulation is bright. Researchers are exploring non- and minimally-invasive ways to engage brain circuits and control seizures through intermittent stimulation of other cranial nerves. Non-invasive devices that don’t require surgery are also being tested in clinical trials.
As of 2021, researchers are also testing a transcranial magnetic stimulation (TMS) device, which attempts to block seizures by creating a magnetic field using a coil placed close to your skull. Similarly, transcranial electrical stimulation (TCS) devices, which use electrodes on the scalp to send electric pulses to the brain, are being tested.
Although these medical devices are still in the development stages, promising results have been seen in those with drug-resistant focal (partial) epilepsy.