Responsive Neurostimulation (RNS) is a treatment using a surgically implanted medical device to manage epilepsy. This neuromodulation approach is for adults with focal seizures that have not been controlled by medication. The device functions like a heart pacemaker, but instead monitors brain activity to detect and stop seizures as they begin. It provides therapy tailored to an individual’s specific seizure patterns.
Understanding the RNS System Components
The RNS System includes the neurostimulator, a small, battery-powered device surgically placed within the cranium to analyze brain activity and generate electrical stimulation. Connected to the neurostimulator are leads, which are thin, flexible wires with electrodes at their tips. These leads are positioned on the surface of the brain or within deeper brain tissue where seizures originate to continuously monitor brain waves and deliver therapeutic pulses.
The system also includes external equipment for management. A physician uses a dedicated programmer, a computer system with a wireless wand, to set and adjust the parameters for detecting seizure activity and delivering stimulation. The patient is provided with a remote monitor, a laptop-like device used to collect data from the implanted neurostimulator and upload it for their doctor to review.
The Closed-Loop Stimulation Process
The RNS System operates on a closed-loop principle, continuously monitoring brain activity, detecting a seizure’s onset, and responding automatically. The implanted leads constantly record electrocorticographic (ECoG) data, providing a real-time window into the brain’s electrical state. The neurostimulator is programmed by a physician to recognize the unique brain wave patterns that signal the start of a seizure for that specific person.
Once the neurostimulator detects this predefined abnormal electrical activity, it delivers small, brief pulses of electrical stimulation directly to the seizure focus. This stimulation is designed to interrupt the aberrant brain activity, helping to normalize brain waves and prevent a clinical seizure from developing. The entire cycle of detection and response occurs in milliseconds, and the stimulation is typically imperceptible to the patient.
The RNS Candidacy and Implantation Procedure
The treatment is approved for adults aged 18 and over who experience focal epilepsy, where seizures originate from one or two specific areas in the brain. A primary criterion is that the epilepsy is considered drug-resistant, meaning seizures persist despite trials of at least two different anti-seizure medications. Candidates undergo extensive diagnostic testing, including electroencephalogram (EEG) monitoring and imaging tests like MRI, to pinpoint the seizure onset zone(s). The system is an option for individuals when resective surgery is not feasible, perhaps because the seizure focus is in a sensitive area of the brain or involves multiple locations.
The implantation is a neurosurgical procedure performed under general anesthesia that takes a few hours. The surgeon makes an incision in the scalp and creates a space in the skull to fit the neurostimulator so it sits flush with the bone. Using imaging for guidance, the surgeon then places the leads at the predetermined seizure source. A hospital stay of one to two days is common, with a return to normal activities within a few days.
Long-Term Management and Lifestyle
Life after RNS implantation involves a collaborative relationship with the medical team. Following surgery, the device is initially set to only monitor brain activity. The stimulation is activated later, and the system requires gradual programming by a neurologist to treat an individual’s unique seizure patterns. Using the remote monitor to upload daily information from the neurostimulator is a routine part of living with the device, allowing the physician to refine settings for better seizure control.
There are practical considerations for individuals with an RNS System. The neurostimulator’s battery is not rechargeable and has an estimated life of up to 11 years, requiring an outpatient procedure for replacement. MRI scans may be possible but only under specific conditions outlined by the manufacturer. Patients also receive a magnet to swipe over their device when they experience a seizure, which marks the event’s data for their doctor’s review.