Story by: David Steen Martin on November 19, 2021
Using electrical stimulation to treat seizures in children — neuromodulation — is a potentially life-changing treatment option for kids with drug-resistant, or refractory, epilepsy.
“Neuromodulation is the alteration of nerve activity through targeted delivery of a stimulus, such as electrical stimulation,” said Ian S. Mutchnick, M.D., a pediatric neurosurgeon at Norton Children’s Neuroscience Institute, affiliated with the UofL School of Medicine.
Small amounts of electricity are designed to block seizures, reduce their severity or frequency, or stop them as they are about to happen. The three main types of neuromodulation to treat epilepsy are responsive nerve stimulation, vagal nerve stimulation and deep brain stimulation.
Responsive nerve stimulation (RNS) uses electrodes to detect seizures as they are about to happen and then delivers a mild electrical current from a stimulator embedded in the skull, with the goal of stopping the seizure. RNS works by looking for abnormal brain activity that indicates the beginning of a seizure. Because the device records brain activity, the data can be downloaded and used to improve RNS over time by fine-tuning which specific brain waves to look for in that individual.
In one study, adult patients with RNS showed a steady decrease in the number of seizures year after year, on average. For three-fourths of these patients, the number of seizures was cut by more than half by the ninth year. More than a quarter of the patients followed in the study had experienced at least one period of more than six months without a seizure.
Vagal nerve stimulation (VNS) typically sends regular, small pulses of electricity to the brain through the vagus nerve. The nerve is wrapped with electrodes in the neck, and the battery-powered stimulator is implanted in the upper left chest. VNS is designed to reduce the number of seizures, as well as their length and severity. Instead of sending regular pulses of electricity, another type of VNS looks for a rapid heart rate, which often signals a seizure, and delivers a stimulation in response to that.
A study following 14 patients with VNS that sent out regular pulses found a 50% reduction in seizure frequency after 14 to 35 months, on average. Two (14%) of the patients were seizure-free for over a year.
Deep brain stimulation (DBS) delivers a continuous electric current to a precise spot in the brain, with the goal of blocking seizure activity altogether.
For children with drug-resistant epilepsy who have DBS, the change can be dramatic. One study of 13 children in Mexico who received deep brain stimulation for a type of epilepsy called Lennox-Gastaut syndrome showed an overall 80% seizure reduction. Although three of the children showed no improvement, two were seizure-free. The remaining eight showed significant improvement.
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For two-thirds of children with epilepsy, medications are effective at reducing seizures. The remaining one-third have drug-resistant epilepsy, meaning they have tried two or more anti-seizure medications without success.
For these children, surgery, a ketogenic diet or implantation of a neuromodulation device are options. Determining which of these is best for a particular child requires a detailed evaluation that can be done at Norton Children’s Neuroscience Institute. A key part of this evaluation often will include the implantation of electrodes directly into the brain in order to better understand where the patient’s seizures originate. To do this, Dr. Mutchnick uses a 3D printed frame, which gets mounted to the patient’s head and guides each electrode to the precise spot. Sometimes, instead of a frame, a precision-guided robot assists with the targeting.
Patients with implanted electrodes are monitored in the pediatric intensive care unit, sometimes for a few weeks. Once the origin of the seizures is determined, the best strategy for helping with the seizures can be determined.