Epilepsy, also known as a seizure disorder, is a condition that can seriously disrupt a patient’s everyday life. About 3.4 million people of all ages in the United States have this neurological disorder. But unlike with other brain-related conditions, about two dozen medications can successfully treat many cases of epilepsy. Although there is no cure, these anti-seizure drugs turn the disease into a chronic, but well-managed condition for many to the point where it barely interferes with life.
But about one-third of patients aren’t so lucky. They experience no relief from anti-seizure drugs and are looking for additional treatment options.
Now they may have found one in a new generation of neurostimulation devices used for epilepsy. In 2018, the Food and Drug Administration (FDA) approved a deep brain stimulation (DBS) device, manufactured by Medtronic, that sends electrical pulses through the brain to reduce the frequency of seizures. (It works by stimulating an important relay station deep in the brain called the thalamus.) And in June 2020, the FDA approved the Percept PC, also from Medtronic. Facilitating more customized therapy, this modified version allows doctors to treat epilepsy and record electrical activity from deep in the brain. (The Percept PC is also approved for other conditions, such as Parkinson’s disease and essential tremor.)
Last year, the Yale Comprehensive Epilepsy Center became the first epilepsy center in the U.S. to implant the device in a patient with epilepsy. As of March 2021, eight epilepsy patients have been implanted with the Percept PC device at Yale.
What is epilepsy?
At the most basic level, everything we think, feel, and do is controlled by brain cells communicating with one another. They send messages through neurotransmitters like dopamine or via electrical pulses that travel through axons—long nerve fibers that connect the cells, or neurons, to each other.
Normally, these electrical signals move between cells in a steady, consistent pattern. When a person has a seizure, however, the pattern is disrupted so that large groups of neurons send messages at the same time. This produces a flood of electrical activity that temporarily prevents areas of the brain responsible for language, memory, emotion, and consciousness from functioning.
“Epilepsy is a sort of electrical activity that builds up over time before it is released and causes abnormality throughout the brain,” says Yale Medicine neurologist Imran Quraishi, MD, PhD.
There are many different types of seizures, with a variety of causes. Focal (partial) epilepsy refers to seizures that start in one part of the brain. In some seizures, the electrical activity stays in that part of the brain and can cause a variety of symptoms including an inability to speak, “spacing out,” and memory lapses. In other seizures, the activity either spreads to or starts on both sides of the brain and can cause a person to pass out, faint, or even stop breathing.
There are many treatment options for patients with focal epilepsy, including medications, surgical resection, laser ablation, dietary therapy, and neurostimulators. In some cases, however, neurostimulation is the only option that is effective, says Dr. Quraishi.
How deep brain stimulation can help with epilepsy
The 2018-approved DBS device uses electrical pulses to regulate the brain’s electrical activity. It’s similar to a pacemaker, which sends electrical signals to keep the heart beating normally.
The device has two components: a neurostimulator, which is surgically implanted in a patient’s chest, and electrodes that are inserted into the brain. The neurostimulator releases electrical pulses through thin wires connected to electrodes that transfer the electricity to an area of the brain called the thalamus.
“The thalamus connects a lot of areas of the brain,” says Lawrence Hirsch, MD, co-director of the Yale Comprehensive Epilepsy Center. “It’s a central networking place for electric signals in the brain. You can think of it like a big airport where flights pass through to connect to other places.” With DBS, electricity inside neurons in the path of an electrical pulse gets turned off. “This helps to make the brain less excitable or less likely to cause seizures,” he adds.
The Percept PC approved last June is Medtronic’s same DBS device, but with one significant difference—it records a patient’s brain signals.
Our goal is to have an app connected to the device that tells patients they have, for example, a 90% chance of having a seizure that day. Yale Medicine neurologist Imran Quraishi, MD, PhD
Using information collected by the Percept PC, Dr. Hirsch explains, neurologists can more precisely adjust the device’s programming. “We may start the pulses at 30 seconds on and five minutes off during a 24-hour cycle and make changes from there,” he says.
So far, the device is only approved for adults with focal epilepsy.
Research shows how the deep brain stimulation device improves symptoms
The FDA approved Medtronic’s 2018 DBS device for epilepsy based on data gathered from the SANTE (Stimulation of the Anterior Nucleus of the Thalamus in Epilepsy) clinical trial. This randomized double-blind study enrolled 110 adults who were experiencing an average of six seizures per month. In the first several months of the trial, half the patients had their device turned on and half did not; neither the patients nor the assessing physicians knew whether the device was on or off. Those with the device turned on had fewer seizures than those with the device off. The benefit continued to increase over time, says Dr. Hirsch.
The study followed patients for seven years. In the first year after the device was implanted, 43% of participants with it had experienced half as many seizures as they’d been having when the study began. After seven years, researchers found that 74% of patients experienced the same reduction in seizure frequency—seizures were cut in half or better, says Dr. Hirsch—according to Medtronic. And in that same seven-year period, patients experienced a median of 75% fewer seizures from their baseline.
More data for more accurate predictions
Neurologists have been collecting patient data from the new Percept PC for several months, but it’s too soon to know if the new device will help patients more than the previous model.
“We’re hoping that by relying on the patient’s seizure patterns from the Percept, we’ll be able to make adjustments more quickly and won’t have to wait years to get the maximum benefit from the device,” Dr. Hirsch says.
You can think of it [the thalamus] like a big airport where flights pass through to connect to other places. Lawrence Hirsch, MD, co-director of the Yale Comprehensive Epilepsy Center
For his part, Dr. Quraishi hopes that when reams of data have been collected from enough people, neurologists may have better insight into how to more accurately predict a patient’s risk of a seizure. This could lead to a significant improvement in quality of life for people with treatment-resistant epilepsy, since being able to forecast one’s daily risk of a seizure would make everyday activities feel less risky.
To give a sense of how this would work, Dr. Quraishi compares the device to common apps we all use to plan our activities. “Right now, before you go outside you check a weather app,” Dr. Quraishi says. “Our goal is to have an app connected to the device that tells patients they have, for example, a 90% chance of having a seizure that day.” If that’s the case, patients would know they might want to stay home and get extra rest, he adds.
Or even better, says Dr. Hirsch, they may be able to take extra medications based on the prediction algorithm to prevent that seizure from even happening.